Diagnosis of HIV infection is essential for effective treatment. To diagnose AIDS, a standard patient examination procedure is performed. It consists of 2 stages:
- screening;
- immune blotting.
To make a diagnosis, PCR is additionally prescribed, express testing.
ELISA
The initial diagnosis of AIDS is based on the use of laboratory HIV proteins that trap specific antibodies. After their contact with the enzymes of the test system, the color of the indicator changes. Then the changed color scheme is processed using special equipment, which determines the test result.
A similar laboratory diagnosis of HIV infection shows a result 21 days after infection. With the help of ELISA it is impossible to determine the presence of the virus. This diagnostic method helps to detect the production of antibodies to the virus. A similar process can be observed 2-6 weeks after infection.
Specialists distinguish 4 generations of ELISA systems with different sensitivities. Doctors often use 3rd and 4th generation tests. These systems are based on recombinant proteins or peptides of synthetic origin, which have significant accuracy and specificity. ELISA is used to detect, monitor the spread of the virus, which ensures safety when checking donated blood. The accuracy of such systems ranges from 93-99%. Tests issued in Western Europe are more sensitive. To perform diagnostics, the laboratory assistant takes venous blood (5 ml). For 8 hours before the study, it is recommended to refuse to eat. The study is more often carried out in the morning.
Data decryption
It will take 10 days to receive test results. If the result is negative, then the patient is not infected. In this case, treatment is not prescribed. A false negative result is detected:
- up to 3 weeks after infection;
- in the last stage of AIDS with a low immune system;
- with improper blood preparation.
If the result is positive, then the patient is infected. In this case, IB is carried out. A false positive result indicates the presence of concomitant diseases and improperly performed blood preparation. If testing is indicated for pregnant women, then in the collected material the doctor can detect non-specific antibodies, the production of which is not associated with the virus. The collected material is examined in a reference or arbitration laboratory. If the retest result is negative, then the first result is false. In this case, IB is not carried out.
Performing an immune blot
Treatment for AIDS is given when a positive immune blotting result is obtained. This diagnostic method is carried out using a nitrocellulose strip on which viral proteins are applied. For IB, venous blood is used, which is then processed. The proteins found in whey are divided into groups based on their charge and molecular weight. To carry out this process, special equipment is used.
If there are antibodies to the virus in the test material, the corresponding lines appear on the strip. A positive IB indicates that the patient is HIV positive. A doubtful result is detected at the initial stages of infection, with tuberculosis and oncology, in pregnant women. In such cases, it is recommended to repeat the IB.
An indeterminate IB result indicates the presence of one or more proteins to the virus in the immunoblot. A similar picture is observed with a recent infection, when there is a small amount of antibodies to the infection in the blood. In this case, the IB will be positive after a while. The uncertain result of this study may be due to the absence of HIV infection in hepatitis, chronic metabolic diseases, during pregnancy. In this case, the IB will become negative or specialists will identify the cause of the uncertain result in the patient.
PCR study
The protective system is affected against the background of the introduction of the virus into the human body. The incubation period is typically 3 months. Therefore, after sexual contact with an HIV-infected partner, it is recommended to undergo PCR diagnostics. It will allow you to determine the RNA of the virus. The period during which it is recommended to undergo such a study is 8-24 months.
For the final diagnosis, regular blood donation for HIV is indicated (1 time in 3 months). Due to its high sensitivity, this examination allows to detect the virus 10 days after infection. A false positive PCR result can also be obtained if another infection is present in the patient's body. PCR research is considered an expensive procedure, as it requires special equipment.
PCR is prescribed to detect the virus in the following individuals:
- a newborn born from an HIV-infected mother;
- patients with questionable IB.
Also, this technique is shown to control the concentration of the virus in the blood and the study of donor blood.
Rapid research methods
Experts include rapid tests to modern methods of diagnosing AIDS. It will take 10-15 minutes to decrypt them. Immunochromatographic tests based on capillary flow provide accurate results. Such testing systems are presented in the form of special strips on which blood or saliva is applied. In the presence of a virus, 2 strips appear on the test after 10 minutes:
- control;
- color.
In this case, the test result is positive. A negative result is indicated by the appearance of one control strip. To confirm the result obtained, an IB is carried out. Based on the general data, the doctor makes a diagnosis and prescribes treatment.
You can detect the virus at home. For this, special express kits are used. OraSure Technologies1 is a system developed in the USA. If a positive result is found after testing, the patient is recommended to undergo a full examination at the medical center.
Examination of the child
Newborn babies who were born from infected mothers are urgently examined. With the help of serological methods, it is impossible to accurately detect the virus in children aged 5-18 months. But the result of such a survey is important when conducting IB.
You can detect infection in children using PCR. The DNA of the virus is detected by a specialist in children of the first month of life. To determine the concentration of pathogen RNA, experts determine the immunodeficiency provirus. For research, the doctor uses whole blood or its dried spot. The material is placed in a test tube with EDTA preservative (proportion 1:20). The sample must be stored at a temperature not exceeding 8°C (for 2 days). Material freezing is not allowed.
To obtain a dry blood sample, the whole liquid is applied to a special paper. The sample can be stored below 8°C. Cards are used for 8 months. A newborn child must be examined, taking material for research, within the following periods:
- 48 hours after birth;
- at the age of 2 months after birth;
- 3-6 months after birth.
If the doctor detected the HIV provirus gene a few hours after the baby was born, then the baby was infected intrauterinely. You can also get the virus during childbirth or while breastfeeding. The results, which indicate the presence of virus DNA in 2 samples, indicate the development of AIDS in the child. Dispensary observation is not required if the results of PCR are negative 4 months after the birth of the baby.
If the test result is negative, but the symptoms of AIDS are present, then it is recommended to consult a doctor. Such a clinic can be triggered by other diseases. Testing is considered the only and 100% method for diagnosing a virus. Even qualified and experienced professionals cannot identify the virus by the symptoms it presents.
If after a while the results of the patient are negative, then there is no HIV in the body.
It does not take into account symptoms. But such a clinical picture may be associated with AIDS phobia. In this case, the help of a psychologist is required. If necessary, the child or adult is prescribed appropriate treatment.
And
If the disease is detected at an early stage and treated immediately, it is possible to stop the transmission of the virus from carriers to healthy people. Also, early detection is relevant for the provision of social, psychological assistance and the possibility of dispensary treatment. To date, a cure for this disease is possible, but on condition that the diagnosis of HIV infection has revealed an early stage of infection. This significantly prolongs the life of patients, which is important for them.
There are a number of symptoms that should alert you and make you go for an examination:
- Frequent, unexplained fatigue;
- Sweating at night;
- Frequent pain in the head area;
- Feverish state, up to about ten days, with a temperature of up to 38.5 C;
- diarrheal manifestations;
- Unreasonable weight loss in a short period of time.
If during the period of diagnosis there will be manifestations of rash, furunculosis and other manifestations, this will facilitate the identification of the disease. Lymphadenopathy or enlarged lymph nodes may indicate a possible infection, most often these are the nodes of the neck, jaw, subclavian, axillary and elbow. Their size is about 2.5 centimeters in diameter. On palpation, pain is not felt, they are of dense elastic content, rarely appear as merging into a conglomerate. With HIV, the nodes most often increase in groups, for a period of more than three months.
Often in the early phases of the disease, neuropsychiatric symptoms occur:
- Anxious behavior and feeling;
- Depressive state;
- Uncertain gait, staggering;
- Deterioration of clarity of vision, its decrease;
- convulsions;
- memory impairment;
- Inadequate actions and actions that are unusual for a person;
- Weakening of feelings;
Signs of the initial phase of HIV, which you should pay attention to:
- Weight loss up to 10%;
- Detection of changes in the mucous membrane (dermatitis, boils, psoriasis, nail fungus, ulcers and gingivitis);
- Herpes in people under 50 years of age;
- Recurrent respiratory tract infections.
The second phase of the disease is deployed by a list of superinfections in immunodeficiency:
- Weight loss by more than 10%;
- Diarrhea lasting more than a month;
- Candidiasis affecting the oral cavity;
- Tuberculous lesions of organs, leukoplakia;
- Neuropathy, Kaposi's sarcoma, herpetic processes;
- Bacterial infections, manifested in severe form;
The last phase of diagnosing the disease may include:
- pneumonia;
- Toxoplasmosis;
- CMV infection;
- Cryptococcosis;
- Herpes manifestations;
- Leukoencephalopathy with multiple foci;
- Histoplasmosis, esophagitis;
- MAC infection;
- Tuberculosis and many other diseases in a more complicated degree.
Laboratory methods- this is the identification of AIDS-associated abnormalities in a patient infected with a secondary immunodeficiency. HIV disease contains 23 nosological types; a syndromic approach to determining a more accurate diagnosis is appropriate.
HIV detection is based on the detection of HIV antibodies and viral antigens, and in some cases HIV proviral DNA and HIV viral RNA are detected (in infants under 1 year of age). the base acts in three directions: the definition of HIV and its components, the detection of anti-HIV, the establishment of changes in the functionality of the immune system. Component of HIV- these are the structural genes gag, pol, and also env, they encode protein translation based on the direct structure of the virus.
Regulatory genes is the union of tat, rev, vif, nyf, vpx and vpr. The gag gene encodes core proteins with initial translation products, pp53 is a precursor protein that tends to cleave into p15, p17 and p24 or p39, followed by cleavage into p17 and p24. The patient develops antibodies to this antigen, acre 24 can be detected in the initial phases of infection, since p24 is more immunogenic than p17.
1. Serological methods detection of antibodies (AT) to HIV is the standard for diagnosing HIV infection (ELISA test systems based on synthetic peptides have almost 100% sensitivity and specificity). ELISA allows you to detect HIV AG, which may be indicators of early infection or vice versa late - advanced development of HIV infection (p24 AG)
2. Confirmatory tests— immunoblotting (IB), indirect immunofluorescence (NIF) and radioimmunoprecipitation (RIP).
a) WHO recommends that sera be considered positive if there are antibodies in IB to two envelope proteins and to one of the internal proteins of HIV. Patients who are positive for ELISA but have indeterminate IB results should be examined clinically and evaluated by other means, medical examination, immunologically and after 3 to 6 months their blood serum should be tested for antibodies to HIV.
b) indirect immunofluorescence (NIF) method - used as a confirmatory test in many laboratories or as a screening test.
c) radioimmunoprecipitation is a highly sensitive and specific method based on the use of amino acids labeled with radioactive isotopes. The method is highly sensitive for detecting antibodies to surface proteins and is therefore highly specific, since these components of the virus are present in almost all HIV-infected people after seroconversion.
3. Molecular biological methods: method of molecular hybridization of nucleic acids, PCR
1) as an alternative and additional confirmatory method for detecting the presence of a virus in the body in relation to serological laboratory diagnostic methods;
2) as the first method of specific analysis in the diagnosis of early HIV infection, when specific antiviral antibodies are not yet available;
3) for the diagnosis of HIV infection in newborns from HIV-infected mothers;
4) to determine the viral load and prescribe specific antiretroviral therapy and monitor its implementation;
5) as a clarifying method in case of unclear serological results and in case of discrepancy between serological and cultural analyzes;
6) in the study of sexual partners of HIV-infected persons;
7) as a method of differential diagnosis of HIV-1 and HIV-2;
4. Virological method.
1. Principles of antiretroviral therapy: treatment should begin before the development of significant immunodeficiency; initial therapy should include combinations of at least three drugs; modification of therapy should consist in the replacement or connection of at least two new drugs; it is essential to measure the level of CD4+ cells and viral load; a reduction in viral load below the detection limit of sensitive assays reflects the optimal effect of treatment.
2. There are three groups of modern antiretroviral drugs:
a) nucleoside reverse transcriptase inhibitors (NRTIs): zidovudine (azidothymidine, retrovir); didanosine (ddI, videx); zalcitabine (ddC, chivid); stavudine (Zerit, d4T); lamivudine (3TC, epivir); abacavir; adefovir; combivir (zidovudine + abacavir); trizivir (zidovudine + lamivudine + abacavir); adefovir (nucleotide reverse transcriptase inhibitors).
b) non-nucleoside reverse transcriptase inhibitors (NNRTIs): delaverdin (rescriptor); nevirapine (viramune); ifavirenz.
c) protease inhibitors (PI): saquinavir; ritonavir (norvir); indinavir (crixivan); nelfinavir (viracept); amprenavir (agenase); lopinavir (aluviran); kaletra (lopinavir + ritonavir).
3. Monotherapy with any drug cannot provide a sufficiently pronounced and long-term suppression of HIV replication. Moreover, with monotherapy, the risk of the emergence of resistant strains and the development of cross-resistance to drugs of the same group is increased. The only exception is the use of zidovudine as monotherapy to reduce the risk of perinatal transmission of HIV.
4. The most important criterion for the effectiveness of therapy is the dynamics of the viral load, which should be determined: without treatment - every 6-12 months, during treatment - every 3-6 months, and also 4-8 weeks after the start of antiviral therapy.
In addition to antiretroviral therapy, therapy for secondary diseases that have joined is necessary.
34.3 AIDS (clinical variants, opportunistic diseases).
opportunistic diseases- severe, progressive diseases that develop against the background of increasing immunosuppression and do not occur in a person with a normally functioning immune system (AIDS-indicator diseases).
a) the first group- these are diseases that are inherent only in severe immunodeficiency (CD4+ level< 200 кл/мкл) и поэтому определяют клинический диагноз: 1. Кандидоз пищевода, трахеи, бронхов. 2. Внелегочный криптококкоз. 3. Криптоспоридиоз с диареей более 1 месяца. 4. Цитомегаловирусная инфекция с поражением различных органов, помимо печени, селезенки или лимфоузлов. 5. Инфекции, обусловленные вирусом простого герпеса, проявляющиеся язвами на коже и слизистых оболочках. 6. Саркома Капоши у лиц, моложе 60 лет. 7. Первичная лимфома мозга у лиц, моложе 60 лет. 8. Лимфоцитарная интерстициальная пневмония и/или легочная лимфоидная гиперплазия у детей в возрасте до 12 лет. 9. Диссеминированная инфекция, вызванная атипичными микобактериями с внелегочной локализацией. 10. Пневмоцистная пневмония. 11. Прогрессирующая многоочаговая лейкоэнцефалопатия. 12. Токсоплазмоз с поражением головного мозга, легких, глаз у больного старше 1 месяца.
b) second group- diseases that can develop both against the background of severe immunodeficiency, and in some cases without it: 1. Bacterial infections, combined or recurrent in children under 13 years of age (more than two cases in 2 years of observation): bones or joints, abscesses caused by Haemophilus influenzae, streptococci. 2. Disseminated coccidioidomycosis (extrapulmonary localization). 3. HIV encephalopathy 4. Disseminated histoplasmosis with extrapulmonary localization. 5. Isosporiasis with diarrhea persisting for more than 1 month. 6. Kaposi's sarcoma in people of any age. 7. B-cell lymphomas (with the exception of Hodgkin's disease) or lymphomas of unknown immunophenotype. 8. Tuberculosis extrapulmonary. 9. Salmonella septicemia recurrent. 10. HIV dystrophy.
The most common are pneumocystis pneumonia, cryptococcal meningoencephalitis, generalized cytomegalovirus infection (encephalitis, retinitis, esophagitis, hepatitis, colitis), sepsis of mixed etiology, generalized form of Kaposi's sarcoma, pulmonary tuberculosis.
All these diseases occur with damage to one or more organs and systems: the brain, lungs, liver, gastrointestinal tract and are of a severe progressive nature. AIDS-indicator diseases appear in various combinations, and even adequate therapy does not bring the expected effect.
Clinical variants of AIDS: infectious-, neuro-, onco-AIDS, depending on the prevalence of different clinics.
HIV: diagnosis and treatment, prevention
Acquired immunodeficiency syndrome has been one of the key problems of modern society for more than forty years. Therefore, HIV diagnosis is now attracting a lot of attention and resources. After all, the sooner a virus that destroys the body's immune system is detected, the higher the chances of avoiding a fatal outcome will be.
Under the abbreviation HIV lies the definition of the human immunodeficiency virus - one of the most dangerous among the existing ones. Under its influence, there is a deep inhibition of all the protective properties of the body. This, in turn, leads to the emergence of various malignant tumors and secondary infections.
HIV infection can progress in different ways. Sometimes the disease destroys a person in 3-4 years, in some cases it can last more than 20 years. It is worth knowing that this virus is unstable and quickly dies if it is outside the host's body.
HIV can be transmitted artificially, by blood contact and through the biocontact mechanism.
If there was a single contact with a carrier of the virus, then the risk of infection will be low, but with constant interaction it increases significantly. Diagnosis of HIV infection is something that cannot be neglected, especially when changing sexual partners
Pay attention to the parenteral route of infection. It can occur during blood transfusions of contaminated blood, injections using needles that are contaminated with the blood of HIV-infected people, as well as during non-sterile medical manipulations (tattoos, piercings, dental procedures using instruments that have not been properly processed).
At the same time, it is worth knowing that there is no need to be afraid of contact-household transmission of the virus. But the fact remains: a person has a high susceptibility to HIV infection. And if a subject over the age of 35 becomes infected, then the development of AIDS occurs significantly faster than in those who have not yet overcome the thirty-year milestone.
Of course, the best way to identify a problem, or lack of it, is to diagnose HIV infection. But what reasons can a person leading a healthy lifestyle have to go and check himself for the fact of infection? Naturally, such an initiative should be justified by something. Therefore, it is important to know what symptoms may indicate destructive processes that depress the immune system.
The stage of incubation of the virus without a blood test is unlikely to be detected, since the body at this time still does not react to hostile elements in any way.
The second stage (primary manifestations) without the help of a doctor can also go unnoticed. But sometimes there is an active replication of the virus, and the body begins to react to this - fever, various polymorphic rashes, lien syndrome and pharyngitis are noted. At the second stage, it is possible to attach such secondary diseases as herpes, fungal infections, pneumonia, etc.
The third, latent stage is characterized by a gradual increase in immunodeficiency. Due to the fact that the cells of the defense system die, the dynamics of their production increases, and this makes it possible to compensate for tangible losses. At this stage, several lymph nodes belonging to different systems may become inflamed. But strong painful sensations are not observed. On average, the latent period lasts from 6 to 7 years, but can be delayed up to 20.
During the stage of secondary diseases, which is the fourth, there are concomitant infections of fungal, bacterial protozoal, viral origin, as well as malignant tumors. All this occurs against the background of severe immunodeficiency.
Methods for diagnosing HIV infection
Speaking about the deep inhibition of the body's defense mechanisms due to exposure to the virus, it is worth noting that the future of the patient in this case directly depends on timely and accurate diagnosis.
To do this, in modern medicine, various test systems are used, which are based on immunochemiluminescent, as well as enzyme immunoassay. These techniques make it possible to determine the presence of antibodies belonging to different classes. This result helps to significantly increase the information content of methods of analytical, clinical specificity and sensitivity when working with infectious diseases.
It is also interesting that it was the polymerase chain reaction method that made it possible to bring HIV diagnostics to a fundamentally new level. A variety of biological materials are suitable as a material for research: blood plasma, biopsy, scraping, serum, cerebrospinal or pleural fluid.
If we talk about laboratory research methods, they are primarily focused on identifying several key diseases. We are talking about HIV infection, tuberculosis, all sexually transmitted infections, and viral hepatitis.
Molecular genetic and serological tests are also used to identify the immunodeficiency virus. In the first case, the RNA of the virus and the DNA of the provirus are determined, in the second case, antibodies to HIV are analyzed and the P24 antigen is detected.
In clinics that use, so to speak, classical diagnostic methods, a standard protocol for serological testing is predominantly used.
Early HIV Diagnosis
This type of determination of the fact of infection is necessary in order to identify the threat of damage to the immune system as early as possible. This, firstly, avoids the spread of infection, and secondly, to influence the disease in the initial stage.
If we consider the example of Russia, then the clinical classification of HIV infection was introduced in the army and navy of the Russian Federation. This has yielded positive results: the process of early clinical diagnosis has become much easier.
Headache, night sweats and unmotivated fatigue can be identified as common symptoms indicating a possible damage to the immune system. It is also possible the development of fever, accompanied by signs of tonsillitis. This means that the temperature rises to 38 degrees and above, and at the same time the palatine tonsils increase, and pain also appears during swallowing. All this is complemented by rapid weight loss. However, these symptoms are often complex.
In some cases, HIV infection in the early stages can manifest itself in the form of various changes in the skin condition. We are talking about spots, roseola, pustules, furunculosis, etc. Early HIV diagnosis also includes working with symptoms such as generalized or limited enlargement of peripheral lymph nodes.
If there is a simultaneous growth of several lymph nodes, lasting for three months or more, and in different groups, with the exception of the inguinal region, then there is every reason to suspect a virus of the human immune system.
Speaking about the diagnosis in a later period, you need to pay attention to the manifestation of secondary immunodeficiency, which often occurs under the guise of various clinical symptoms. These are the following manifestations:
- unmotivated generalized peripheral lymphadenopathy;
- arthralgia of unknown etiology, which has an undulating course;
- SARS (ARVI), inflammatory lesions of the lungs and respiratory tract, which make themselves felt quite often;
- fever of unknown origin and prolonged subfebrile condition;
- general intoxication, which manifests itself through unmotivated weakness, fatigue, lethargy, etc.
- early diagnosis of HIV infection;
- clarification in the presence of questionable results as a result of immunoblotting studies;
- identification of a specific stage of the disease;
- monitoring the effectiveness of treatment aimed at suppressing the virus.
Late-stage HIV diagnosis includes screening for a disease such as Kaposi's sarcoma, which is manifested by the appearance of multiple neoplasms, often in the upper body in young people, followed by dynamic development and metastasis.
polymerase chain reaction
Considering the various methods for diagnosing HIV infection, this should be given special attention. It should immediately be noted that this blood test can be aimed at quantitative and qualitative characteristics.
The following tasks can be defined as the goal of this method of detecting a virus:
If we talk about primary infection, it should be noted that this technique allows you to determine the HIV RNA in the patient's blood after 14 days from the moment of infection. This is a very good result. In this case, the outcome of the study itself will have a qualitative expression: either positive (the virus is present) or negative.
Quantification by PCR
This type of polymerase chain reaction is used to determine the likely rate of development of AIDS and predict the patient's life expectancy.
Quantification of HIV RNA cells in the blood makes it possible to understand when the disease goes into the clinical stage.
It is worth paying attention to the fact that the methods of laboratory diagnosis of HIV give a more accurate result if the biomaterial required for analysis is determined correctly, and its sampling is carried out correctly.
In order to carry out qualitative monitoring of the infected, it is necessary (if possible) to use an integrated approach to the study of the patient's immune status. We are talking about the quantitative and functional determination of all parts of the defense system: cellular, humoral immunity and nonspecific resistance as such.
Laboratory diagnostics
Increasingly, in modern laboratory conditions, a multi-stage method for assessing the state of the immune system is used. This technique often involves the determination of a subpopulation of immunoglobulins, lymphocytes in the blood. This means that the ratio of CD4/CD8 cells is taken into account. If the result shows less than 1.0, then there is reason to suspect immunodeficiency.
Laboratory diagnosis of HIV infection should include this test without fail, since this virus is characterized by selective damage to CD4 lymphocytes, which leads to a noticeable violation of the ratio mentioned above (less than 1.0).
To assess the immunological status, physicians can conduct a test for the presence of "gross" or general defects in the system of humoral and cellular immunity. We are talking about hypogammaglobulinemia or hypergammaglobulinemia in the terminal stage, as well as a decrease in the production of cytokines, an increase in the concentration of circulating immune complexes, a weakening of the response of lymphocytes to mitogens and antigens.
It is worth paying attention to the fact that the laboratory diagnosis of HIV has two key stages:
- Screening laboratory. If a positive result was obtained in the ELISA (enzymatic immunoassay), then it is repeated two more times in the same system and without changing the serum. In the event that two of the three examinations lead to the detection of the influence of the virus, the serum is sent for further analysis to the reference laboratory.
- The second stage, which includes the methods of laboratory diagnosis of HIV infection, is the determination of the state of the immune system. It is carried out in the reference laboratory mentioned above. Here, the positive serum is again examined in ELISA, but using a different test system, which differs from the previous composition of antigens, antibodies, or the format of the tests themselves. When determining a negative result, a second study is carried out in the third test system. If the impact of the virus was not detected in the end, then the absence of HIV infection is recorded. But with a positive result, the serum is examined in a linear or immune blot.
Ultimately, such an algorithm leads to positive, neutral, or negative results.
Every citizen should know that HIV diagnostics is available to him. AIDS can be identified in private, municipal or public health settings.
Naturally, the identification of the virus would be of little use in the absence of various methods of influencing the infection. And although at the moment there is still no vaccine that could completely neutralize the virus, competent diagnosis, HIV treatment and subsequent prevention can significantly improve the patient's condition, thereby extending his life. This thesis confirms the fact that the average life expectancy of men who started timely HIV treatment is 38 years. Women who begin the fight against the immunodeficiency virus live an average of 41 years.
Once the diagnosis has been made, HIV treatment is reduced to the use of several techniques. Active antiretroviral therapy, also known as HAART, can be identified as one of the most common. If this type of treatment is applied in time and correctly, then it is possible to significantly slow down the development of AIDS or stop it altogether.
The essence of HAART is that several pharmaceutical preparations are used simultaneously, the purpose of which is to influence various mechanisms of the development of the immunodeficiency virus.
After various methods of diagnosing HIV have determined the fact of infection, drugs can be used that have the following types of effects:
It is difficult to overestimate the importance of such measures to influence the disease as the diagnosis, treatment, and prevention of HIV infection. Therefore, the best thing that can be done after a positive result of the study for infection is to immediately begin to fight the disease. As another method that will help to do this, virological treatment can be determined.
In this case, we are talking about the use of drugs that do not allow the virus to attach to the T-lymphocyte and get inside the body. These drugs are called penetration inhibitors. A specific example is Cellzentry.
Viral protease inhibitors can be used to suppress HIV. The purpose of this group of drugs is to prevent infection of new lymphocytes. These are drugs such as Viracept, Reyataz, Kaletra, etc.
The third group of topical drugs are reverse transcriptase inhibitors. They are needed to block the enzyme that allows the RNA of the virus to multiply in the nucleus of the lymphocyte. Such methods can significantly affect a problem such as HIV infection. Diagnosis, treatment and prevention of AIDS is the business of qualified doctors, so the algorithm for using drugs should be made by them.
If necessary, immunological and clinical effects can also be used.
The World Health Organization suggests the following methods of fighting HIV infection:
In order for HIV diagnostics not to reveal the presence of the virus, you need to follow simple safety rules:
Thanks to the fact that HIV diagnosis is not standing still, thousands of people get the opportunity to start treatment on time and significantly increase life expectancy. The main thing is not to ignore the obvious symptoms and not be afraid to go to the doctor.
Laboratory diagnosis of HIV infection
The following are subject to testing for HIV infection:
2. Persons with suspected or confirmed diagnosis: bacterial infection in children under 13 years of age, multiple and recurrent; candidiasis of the esophagus, trachea, bronchi or lungs; cervical invasive cancer; disseminated or extrapulmonary coccidioidomycosis; extrapulmonary cryptococcosis; cryptosporidiosis with diarrhea for 1 month or more; cytomegalovirus lesions of other organs, except for the liver, spleen, lymph nodes in patients older than 1 month; cytomegalovirus retinitis with loss of vision; herpetic infection that causes multifocal ulcers that do not heal within 1 month, or bronchitis, pneumonia, esophagitis; histoplasmosis disseminated or extrapulmonary; isosporiasis with diarrhea for more than 1 month; tuberculosis widespread or extrapulmonary; pulmonary tuberculosis in adults or adolescents over 13 years of age; extrapulmonary tuberculosis; other disease caused by mycobacteria, except M. tuberculosis disseminated or extrapulmonary; pneumonia caused by pneumocystis; progressive multifocal leukoencephalopathy; salmonella (except Salmonella typhi) septicemia, recurrent; brain toxoilase in children older than 1 month; Kaposi's sarcomas; lymphoid interstitial pneumonia in children under 13 years of age; Burkitt's lymphoma; immunoblastic lymphoma; primary brain lymphoma; wasting syndrome, hepatitis B, carriage of HBsAg; infectious mononucleosis; recurrent herpes zoster in persons over 60 years of age; sexually transmitted diseases.
In a highly specialized laboratory are carried out:
a) determination of antibodies, antigens and immune complexes circulating in the blood; cultivation of the virus, detection of its genomic material and enzymes;
b) assessment of the functions of the cellular link of the immune system. The main role belongs to the methods of serological diagnostics aimed at the determination of antibodies, as well as pathogen antigens in the blood and other body fluids.
Testing for antibodies to HIV is carried out in order to:
a) safety of blood transfusions and transplantations;
b) surveillance, testing to monitor the prevalence of HIV infection and study the dynamics of its prevalence in a particular population;
c) diagnosis of HIV infection, i.e. voluntary testing of blood serum of practically healthy people or patients with various clinical signs and symptoms similar to HIV infection or AIDS.
The system for laboratory diagnosis of HIV infection is based on a three-stage principle. The first stage is screening, designed to perform primary blood tests for the presence of antibodies to HIV proteins. The second stage is referential - it allows using special methodological techniques to clarify (confirm) the primary positive result obtained at the screening stage. The third stage - expert, is intended for the final verification of the presence and specificity of HIV infection markers identified at the previous stages of laboratory diagnostics. The need for several stages of laboratory diagnostics is primarily due to economic considerations.
In practice, several tests are used to identify HIV-infected people with a sufficient degree of certainty:
ELISA (ELISA) test (enzyme-linked immunosorbent assay) for detecting the first level is characterized by high sensitivity, although less specificity than the following;
Immune blot (Western-blot), a very specific and most used test to differentiate between HIV-1 and HIV-2;
Antigenemia p25-test, effective in the initial stages of infection;
Polymerase chain reaction (PCR).
In cases of mass screening of blood samples, it is recommended to test mixtures of sera from a group of subjects, compiled in such a way that the final dilution of each sample does not exceed 1:100. If the serum-current mixture is positive, each serum of the positive mixture is tested. This method does not lead to loss of sensitivity in both ELISA and immunoblot, but reduces labor costs and the cost of the initial examination by 60-80%.
In the primary serodiagnosis of HIV infection, total antibodies are determined using screening screening tests - ELISA and agglutination reactions. At the second (arbitration) stage, a more complex test is used - an immunoblot, which allows not only to confirm or reject the initial conclusion, but also to do this at the level of determining antibodies to individual proteins of the virus.
Linked immunosorbent assay(ELISA) is the main and most widely used method for determining antibodies to HIV. But the disadvantages of using ELISA in the serodiagnosis of HIV infection include frequent false positive results. In this regard, the result in the ELISA is not a basis for concluding that the subject is HIV-seropositive. This is due to insufficient purification of the immunosorbent from ballast proteins; spontaneous binding of serum antibodies to plastic, if its areas not occupied by the immunosorbent are insufficiently blocked or not blocked by a completely special neutral protein; cross-interaction with HIV proteins of the immunosorbent of various proteins present in the blood of individuals with certain, more often autoimmune pathological processes such as multiple sclerosis, SLE, tuberculosis; with frequent donation, infectious and oncological diseases, burns, pregnancy, repeated blood transfusions, transplantation of organs, tissues, as well as persons on hemodialysis; with the presence of rheumatoid factor in the blood, often provoking HIV false-positive reactions; the presence in the blood of the examined people of antibodies to HIV gag proteins and, above all, to the p24 protein (obviously, antibodies are formed to exogenous or endogenous retroviruses that have not yet been identified). Since anti-p24 is synthesized without fail in the early stages of HIV seroconversion, further immunological monitoring of individuals with antibodies to HIV gag proteins is carried out, as well as their removal from donation.
The sensitivity and specificity of enzyme immunoassay is constantly increasing. As a result, the fourth-generation ELISA is not inferior in its diagnostic capabilities to immune blotting and can be used not only at the screening, but also at the confirmatory stage of diagnosing HIV infection [Smolskaya T. T., 1997].
Immunoblotting is the final method of serological diagnostics, allowing to make a final conclusion about the HIV-positivity or negativity of the subject.
There is a clear correlation between the results of the study of sera in immunoblot and ELISA - twice positive in ELISA with different test systems, serum in 97-98% of cases then turn out to be HIV-positive in immunoblot. If the sera turned out to be positive in ELISA in only one of the two test systems used, they are detected positive in the immunoblot only in 4% of cases. In 5% of cases, when conducting confirmatory studies in people with positive data, the ELISA immunoblot can give “indeterminate” results, and among them, in about 20% of cases, antibodies to HIV-1 gag proteins (p55, p25, p18 ). The presence of antibodies only to HIV-1 gag proteins is a reason for additional examination of blood serum for HIV-2 infection.
The evaluation of the results of immunoblotting is carried out strictly in accordance with the instructions attached to the test system. In the absence of guidance on the interpretation of results, the WHO criteria should be used.
Upon receipt of positive test results at the reference stage of laboratory diagnosis of HIV infection and a negative result of the study by the method of immune blotting, a mandatory repeated expert diagnosis is performed 6 months after the first examination.
If the results of immunoblotting 12 months after the study of the first sample remain negative or indeterminate, then in the absence of risk factors, clinical symptoms or other factors associated with HIV infection, the subject is removed from dispensary observation.
Among serological methods, in case of indeterminate results, the immunoblot is used as an expert diagnosis. radioimmunoprecipitation(RIP). It is based on the use of viral proteins labeled with radioactive iodine, and precipitates are detected using beta counters. The disadvantages of the method include the high cost of equipment, the need to equip special rooms for these purposes.
Persons diagnosed with HIV infection are subject to constant dynamic monitoring with mandatory laboratory examination every 6 months.
Polymerase chain reaction (PCR) reveals premultiplied nucleotide sequences specific for the genome of a given pathogen. Isolated multiplication of a gene or its fragment, called amplification, PCR makes it possible to carry out in vitro using the enzyme thermostable DNA polymerase. For 2-3 hours, PCR allows you to get millions of copies of a specific section of the virus. During HIV infection, from cellular RNA, including the RNA of the virus, if it was reproduced in the cell or was integrated into its genome, using reverse transcription and hybridization with labeled oligonucleotide "probes", a sufficient amount of proviral DNA is obtained for analysis, which is detected and characterized quantitatively , as well as in relation to belonging to the HIV genome, establishing the homology of DNA and virus-specific amino acid sequences by a radioactive or other label of the probe. The sensitivity of PCR is the detection of viral genes in one of five thousand cells.
PCR, including quantitative, can only be used to determine the viral load on plasma to resolve the issue of starting drug treatment for a patient or changing antiretroviral drugs. PCR cannot be recommended for diagnosing HIV infection, since even the most cutting-edge methods of its formulation and reagents make it possible to determine the viral load not lower than a certain level - 50 copies / ml. And the complexity of setting up PCR and its high cost (about $ 200) nullify its large-scale use as a method of everyday laboratory diagnosis of HIV infection. Thus, PCR remains indispensable only for assessing the viral load on plasma in patients with an already established diagnosis of HIV infection in order to resolve the issue of patient therapy.
Schematically, the stages of laboratory diagnosis of HIV infection are shown in Fig. one.
Rice. 1. Stages of laboratory diagnosis of HIV infection
During HIV infection, there is a period of "dark laboratory window" when the amount of anti-HIV antibodies is insufficient for the sensitivity of the test systems. This period ranges from one week to three months from the moment of HIV infection, depending on the level of sensitivity of the test system. Given this phenomenon, difficulties arise when examining donated blood from persons who are in the mentioned period of HIV infection. Therefore, in most countries of the world, a system has been introduced for using blood only after it has been stored for 3-6 months in order to carry out a mandatory re-examination for HIV infection of donors of these doses of blood and its components.
The stage of primary manifestations is characterized by the activity of the replicative process. The resulting viremia and antigenemia cause the formation of specific antibodies of the IgM class: anti-p24, anti-gp41, anti-gp120. The p24 antigen in some of the infected can be detected in the blood by ELISA as early as 2 weeks after infection and can be determined up to the 8th week. Further, in the clinical course of HIV infection, a second rise in the content of the p24 protein in the blood is noted, it falls on the period of the formation of the AIDS stage.
The appearance of complete seroconversion, when a high level of specific antibodies of the IgG class to the structural proteins of HIV gp41, p24, gpl20, is recorded in the peripheral blood, greatly facilitates the diagnosis of HIV infection. Most commercial kits are designed to indicate just such antibodies.
Difficulties in detecting antibodies in HIV-infected patients may arise during periods of massive viremia and antigenemia, when the available specific antibodies in the blood are used up to bind viral particles, and the replicative process is ahead of the production of new antiviral antibodies.
In individuals with an initially weakened immune system, viremia and antigenemia appear earlier and remain at a high level until the outcome of the disease. At the same time, such patients have a low content of free antibodies to HIV, due to two reasons - insufficient production of antibodies by B-lymphocytes and antibody binding of virions and soluble HIV proteins, therefore, to determine infection, test systems with increased sensitivity or modifications of analysis methods are required, providing stage of release of antibodies from immune complexes.
Despite the abundance of specific markers of HIV infection, the most frequently determined is the presence of total antibodies to HIV proteins. The term "total" implies the presence of two classes of antibodies (IgG and IgM) and a wide range of antibodies to various, primarily structural, HIV proteins.
Determination of CD4 cells. The main clinical and laboratory indicator for diagnosing the stage of HIV infection, the degree of destruction of the immune system in patients in everyday life, was the determination of the content of CD4+ lymphocytes: a decrease in the level below 200 cells/mm3 is the main criterion for diagnosing AIDS. It is believed that all HIV-infected individuals with a CD4+ lymphocyte count of 200 cells/mm3 or less require both antiviral therapy and PCP prophylaxis. And although 1/3 of HIV-infected people with a CO4+ lymphocyte count of less than 200 cells/mm3 have no clinical manifestations, experience has shown that they develop symptoms in the next 2 months, so they are all regarded as patients at the AIDS stage.
Diagnosis of HIV infection
How do you know if a person has HIV? The most common method for diagnosing HIV infection is enzyme-linked immunosorbent assay (ELISA). ELISA test systems are used to detect antibodies to HIV in the blood serum.
HIV infection is confirmed by two different tests, a screening test and a confirmation test. Due to their high sensitivity, screening tests may give false positive results. Therefore, usually when an initial positive result is obtained, the same blood sample is taken and the screening test is duplicated a second time, and if it is again positive, only then another type of confirmatory test is performed. Confirmatory tests are only done on blood samples that repeatedly test positive (are "reactive").
The most common screening test is the enzyme immunoassay (ELISA). Usually, immunoblotting is used as a confirmatory test. The combination of two different types of tests ensures that the results obtained are of "high accuracy".
Screening test systems use artificially created HIV proteins that “catch” specific antibodies produced by the body in response to virus proteins. Once the antibodies are caught, they "can be detected by reagents that are applied in conjunction with an indicator, such as an enzyme that causes a color change." Color changes are read by the machine, which determines the result. Immunoblotting works in a similar way, but it uses an electric field that discriminates between different components based on their molecular weight. This makes it possible to identify antibodies to specific viral antigens, which are then depicted on paper as distinguishable "streaks". Modern test systems can detect HIV infection in 3-5 weeks in most people.
If there was a risk of contracting HIV, when can I get tested?
The enzyme immunoassay (ELISA), which is used to diagnose HIV, may not show results until several weeks after infection. This type of analysis does not determine the virus itself, but antibodies to it. In some people, antibodies are present in the blood in sufficient quantities after 2 weeks. However, it takes longer for most people to form antibodies (seroconversion). In order for the test result to be sufficiently reliable, it is necessary that about 3 months have passed since the risky situation. Sometimes the formation of antibodies takes longer - from 3 to 6 months.
If the test result is negative after 3 months, is it necessary to do a second test after 6 months?
In the vast majority of people, the test is quite reliable after 3 months (for most, antibodies appear even earlier). You can completely eliminate the possibility of infection by passing the test after 6 months.
How long do I have to wait for test results?
It depends on the characteristics of the laboratory in which the testing is carried out. The ELISA test can be done within the same day, but in most laboratories this period can be from 1-2 days to 2 weeks. Considering that waiting for results can be a very frustrating period, it is best to clarify this issue in advance, before taking the analysis. You can also find out if weekends and holidays will affect the timing of the test.
How reliable is a positive test result?
Sometimes ELISA has false positive results (in about 1% of cases), the reason for this result can be pregnancy, various viral infections, as well as a simple accident. After receiving a positive result, a more accurate test is needed - an immunoblot, according to the results of which a diagnosis is made. A positive immunoblot result after a positive ELISA is 99.9% reliable - this is the maximum accuracy for any medical test. If the immunoblot is negative, then the first test was false positive, and in fact the person does not have HIV.
What is an indeterminate (doubtful) result?
If the ELISA is positive or negative, then the immunoblot can be positive, negative, or indeterminate. Indeterminate immunoblot result, i.e. the presence in the immunoblot of at least one protein to the virus can be observed if the infection has occurred recently and there are still few antibodies to HIV in the blood, in which case the immunoblot will become positive after a while. Also, an indeterminate result may appear in the absence of HIV infection with hepatitis, some chronic metabolic diseases, or during pregnancy. In this case, either the immunoblot will become negative or the cause of the indeterminate result will be found.
Do I need to take an HIV test when applying for a job?
According to the legislation of the Russian Federation, mandatory HIV testing can be only for blood donors, foreign citizens and stateless persons who wish to enter the territory of the Russian Federation for a period of more than three months, as well as medical personnel working directly with blood; persons in places of detention. All other citizens take an HIV test voluntarily.
HIV infection A disease resulting from infection with the human immunodeficiency virus (HIV).
HIV is an RNA virus belonging to the retrovirus family.
A common property of retroviruses is the presence of an enzyme - reverse transcriptase (revertase), which "removes" a genetically exact copy in the form of DNA from RNA. According to morphology, genome structure and other features, HIV belongs to the family of lentiviruses, that is, viruses of slow infections. The common features of diseases caused by viruses of this family include: a long incubation period that does not have exact dates (from 1 month to 10 years or more); imperceptible, asymptomatic onset of the disease; slowly growing clinical picture; the mediation of pathogenesis through the immune system and the high rate of genetic variability of the virus. All this greatly complicates the diagnosis, treatment and prevention of HIV infection.
There are currently two types of HIV known: HIV-1 and HIV-2. The disease caused by HIV-2 is characterized by slow dynamics and a longer course.
Epidemiology and modes of transmission:
HIV infection is anthroponosis, the only source of the pathogen for a person is a virus carrier and an AIDS patient.
Viral particles (virions) are present in all biological fluids of the body, but in different concentrations. The highest content of the virus is in the blood and seminal fluid.
The virus is transmitted in three ways:
from mother to fetus/newborn.
HIV is not transmitted through normal household contact and airborne droplets. There are no cases of HIV transmission through the bites of blood-sucking insects.
However, the contagiousness of HIV is not as high as that of other STIs. Thus, out of more than 1600 surveyed sexual partners of HIV-infected, only 15% became infected with this virus.
The development of HIV infection is determined by two interacting factors: the main pathogenic property of HIV - to weaken the immune system of an infected person, and the specific immune response of the body that develops during the course of the disease.
HIV is panthropene, but the main target cells for it are T-helpers, which carry hundreds of CD4+ receptor molecules on the membrane. In the body, the virus transforms from a less aggressive state to a more aggressive one, which is expressed in a progressive decrease in the number of CD4+ lymphocytes in the blood up to their complete disappearance and leads to a worsening of the clinical picture.
From the moment of infection to the appearance of specific antiviral antibodies occurs, as a rule, 6-8 weeks. The period between infection and the appearance of detectable antibodies to HIV in the blood serum is called the "window" period.
On the one hand, the immune system is a target for the virus, on the other hand, it itself produces specific antibodies to it. At the same time, autoimmune processes develop in the immune system, which aggravate the process of destruction of cells and tissues of the body.
HIV infection is characterized by the absence of a specific clinical picture, and its diagnosis, as a rule, is made on the basis of a carefully collected anamnesis, in combination with a number of signs confirmed by laboratory diagnostics. In 1983, WHO developed certain criteria by which to establish the presence of HIV infection in the absence of serological diagnostics (criteria "Bangi"). These include:
- loss of body weight by more than 10% of the original;
- chronic diarrhea for more than one month;
- prolonged fever for one month (constant or intermittent).
- persistent cough for more than one month;
- generalized pruritic dermatitis;
- history of herpes zoster;
- chronic progressive or disseminated herpes infection (herpes simplex);
The diagnosis of HIV infection according to these criteria can be made to the patient if he has simultaneously at least two "large" features and one "small" one. Sufficient grounds for the diagnosis of AIDS may be the detection of generalized Kaposi's sarcoma or cryptococcal meningitis in a patient. Due to the low sensitivity and specificity of these criteria, WHO subsequently required serological confirmation of the diagnosis.
Clinical classification of HIV infection:
Stage of primary manifestations:
A. acute febrile phase;
B. asymptomatic phase;
B. persistent generalized lymphadenopathy.
Stage of secondary diseases:
A. Weight loss less than 10 kg, superficial bacterial, viral, fungal lesions of the skin and mucous membranes, herpes zoster, repeated pharyngitis, sinusitis.
B. Progressive weight loss of more than 10 kg, unexplained diarrhea, fever for more than 1 month, hairy leukoplakia, pulmonary tuberculosis, repeated or persistent bacterial, fungal, viral, protozoal lesions of internal organs (without dissemination) or deep lesions of the skin and mucous membranes, repeated and disseminated herpes zoster, localized Kaposi's sarcoma.
The presence of antibodies to HIV depending on the stage of the disease.
Antibodies to HIV in the blood
HIV test result
II. Primary manifestations
B. Asymptomatic phase
III. Secondary diseases
After the virus enters the body, it multiplies in the blood. In 50% of infected individuals during this period, a prodromal state may develop, accompanied by a rise in body temperature to 38.5-39.5 ° C and other mononucleosis-like symptoms and lasting from three to 10 days. This condition passes, resembling the recovery period after an influenza infection.
Starting from the 6-8th week of the disease, there is an increase in the level of antibodies in the blood, that is, seroconversion. During this period, generalized lymphadenopathy and slight immunodeficiency may develop, but in some patients the clinical manifestations of HIV infection are minimal. With a pronounced syndrome of acquired human immunodeficiency (AIDS), there is a rapid development of opportunistic infections of internal organs, the nervous system is affected. On the skin and mucous membranes, activation of the saprophytic flora is observed. Kaposi's sarcoma and other tumors develop. Infections such as tuberculosis, syphilis, deep mycoses, etc. can become more active. Pneumocystis pneumonia is a typical disease for HIV-infected people. In some patients, the liver and spleen are enlarged, which is an unfavorable sign, indicating a rapid progression of the process. There are cerebral forms of HIV infection - such as meningitis caused by yeast fungi, toxoplasmic brain abscesses, acute and subacute encephalitis, isolated brain tumors (lymphomas). Patients may present with various vascular lesions.
The methods of nonspecific diagnostics include the following: determination of the content of T-lymphocyte subpopulations in the blood, assessment of the activity of the reactivity of T-lymphocytes in peripheral blood or biopsy material.
Specific diagnostic methods include:
— detection of provirus DNA or HIV virus RNA in human cells by PCR;
- detection of mature infectious virions in biological fluids and cells;
- determination of soluble proteins of the virus (antigens);
- determination of antibodies to HIV (ELISA, immunoblot, agglutination reaction, radioimmunoprecipitation).
The most common screening diagnostic method is ELISA. A negative result may indicate:
- about the absence of infection;
- about conducting a study before the onset of seroconversion (during the "window" period or during other periods of disappearance of the antibody titer).
Positive results are either true or false. False positives can be obtained when examining patients with chronic infectious, autoimmune or oncological diseases, uninfected pregnant women, patients after blood transfusions and patients with chronic alcoholism. The earliest time for the detection of antibodies to HIV is 3-4 weeks from the date of infection.
Confirmatory analysis. Immunoblot.
After the screening test, all positive results are checked in another ELISA system, and then - in a more sensitive test - immunoblot. Sera confirmed by this test can be considered true positive.
Before conducting an HIV test, the patient must necessarily be consulted (pre-test counseling) on the reasons for which it is necessary to conduct an analysis, and after receiving the result, accordingly, it is necessary to conduct a post-test counseling in order to explain the result of the study. Confidentiality must be observed at all stages of diagnosis and subsequent treatment.
There are four main approaches to the treatment of HIV infection: etiological, immunostimulating, immunoreplacement and pathogenetic (against secondary infections).
Nucleotide analogs or inhibitors of other classes have the ability to suppress the reverse transcriptase of the virus. The first drug for the treatment of AIDS patients was a nucleotide analogue - azidothymidine. The drug causes side effects, affecting primarily hematopoiesis, and in most patients with long-term use (more than 6 months), resistance to it is formed. Currently, more than 10 new drugs are used - inhibitors of proteases and reverse transcriptase. The rapid rate of HIV mutation in the body, accompanied by the emergence of treatment-resistant strains, greatly complicates the process of creating effective drugs.
Only a combined approach can limit the replication of the virus and prevent the development of drug resistance. Triple antiretroviral therapy (a combination of three drugs based on two nucleoside analogues and protease inhibitors) has become the standard.
Diagnosis of HIV infection includes two stages: establishing the actual fact of HIV infection and determining the stage of the disease. The determination of the stage is inextricably followed by the clarification of the nature of the course of the disease, and then the formation of the prognosis in this patient, as well as the choice of treatment tactics.
As you know, the diagnosis of any infectious disease is based on a comparison of epidemiological, clinical and laboratory data, and exaggeration of the value of one of the groups of these data can lead to diagnostic errors.
Epidemiological criteria for HIV infection .
The first step in diagnosing HIV infection is to collect an epidemiological history and other epidemiological data about the patient being examined. The lack of epidemiological data can significantly complicate the diagnosis of HIV infection and impede the implementation of anti-epidemic measures.
Epidemiological criteria can sometimes be decisive in making a diagnosis of HIV infection, but can also be of secondary importance. The criterion for a high probability of infection is the detection in the examined person of such risk factors for infection as the transfusion of donor blood received from an HIV-infected person, the birth of an HIV-infected child by the examined woman. There is a high probability of infection in the case of the birth of the subject from an HIV-infected mother, sexual contact with an HIV-infected person, joint parenteral drug use with an HIV-infected person. A certain risk of infection is found with reliable parenteral interventions that are carried out with instruments that are likely to be contaminated with HIV (i.e. in nosocomial and similar foci of HIV infection with parenteral transmission of HIV).
A noticeable risk of infection can be discussed in cases where the subject reports sexual intercourse or parenteral drug use in areas where HIV is significantly prevalent among the population group to which the subject belongs.
At the same time, sexual intercourse and drug use in areas with a low prevalence of HIV infection does not exclude the possibility of HIV infection.
The absence of reliable risk factors for HIV infection may cast doubt on laboratory data. In such cases, it is recommended to repeat laboratory tests.
Clinical criteria for HIV infection.
Early diagnosis of HIV infection ensures the timely treatment of the patient and the deployment of preventive measures in the outbreak, preventing unintentional transmission of the virus from an infected person to a healthy person. Finally, early diagnosis allows timely clinical examination, psychological assistance, and social rehabilitation. The first successes in the treatment of patients allow, with early diagnosis, to significantly prolong the life of patients and even hope for a cure.
The complexity of early diagnosis based on the clinical picture lies in the non-specificity, polymorphism of symptoms in stage II, not to mention the absence of a clinic in stage I. Nevertheless, in all cases of unmotivated fatigue, the presence of night sweats, headache, especially against the background of short-term fever ( 3-10 days) with a temperature of 38-38.50 C, accompanied by tonsillitis, prolonged diarrheal syndrome, weight loss in a short time, it is necessary first of all to exclude HIV infection. The diagnosis during this period is helped by the identification of a variety of skin rashes (spots, papules, roseola, pustules) or furunculosis during an objective examination. The presence of lymphadenopathy, even in cases of an increase in one group of lymph nodes, and even more so with a generalized one, is more likely to suspect clinically HIV infection. The disease is especially characterized by an increase in the posterior cervical, submandibular, supra- and subclavian, axillary and ulnar lymph nodes. As a rule, they increase in size up to 2-5 cm in diameter, are painless, densely elastic in consistency, occasionally merge into a conglomerate. It is very typical for HIV infection to increase more than one node, more than one group (with the exception of the inguinal), lasting over 3 months.
Often in the early phase of the disease, the presence of psycho-neurological symptoms: anxiety, depression, unsteady gait, decreased visual acuity, convulsive seizures with signs of damage to the psycho-emotional sphere (memory impairment, forgetfulness, inappropriate behavior, dulling of emotions). To the most characteristic features early stages of HIV infection include:
1. Less than 10% weight loss;
2. Changes in the skin and mucous membranes (seborrheic dermatitis, folliculitis, prurigo, psoriasis, fungal nail infections, recurrent oral ulcers, necrotizing gingivitis);
3 . Herpes zoster in persons under 50 years of age;
4. Recurrent infections of the upper respiratory tract;
IN intermediate stage diseases characterized by a clinic of extended superinfection, formed as a result of immunodeficiency, are most characteristic:
1 . Progressive weight loss over 10%;
2 . Diarrhea of unknown origin, lasting over 1 month;
3 . oral candidiasis;
4 . Leukoplakia;
5. Pulmonary tuberculosis;
6. Peripheral neuropathy;
7. Localized forms of Kaposi's sarcoma;
8. Disseminating herpes zoster;
9. Severe, recurrent bacterial infection (pneumonia, sinusitis, pyomyositis).
For late stage, allowing to diagnose HIV infection, or, in any case, to carry out differential diagnosis, include:
1. Pneumocystis pneumonia;
2 . Toxoplasmosis;
3. Cryptococcosis;
4. CMV infection;
5. Herpes simplex;
6. Progressive multifocal leukoencephalopathy;
7. Histoplasmosis;
8. Candida esophagitis;
9. MAC infection;
10. Salmonella septicemia;
11. Extrapulmonary tuberculosis;
12. Lymphoma, Kaposi's sarcoma;
13. cachexia;
14. HIV encephalopathy.
In 1988, the WHO proposed for the purpose of clinical diagnosis to carry out symptom score available in a patient suspected of HIV infection:
Persistent generalized lymphadenopathy 0
Changes in the skin and mucous membranes 1
Weight loss 1
Severe fatigue 1
Herpes simplex 2
Diarrhea lasting more than 1 month. 4
Fever lasting more than 1 month. 4
Weight loss over 10% 4
Pulmonary tuberculosis 5
Recurrent bacterial infection 5
Oral leukoplakia 5
Stomatitis, thrush of the mouth 5
Localized Kaposi's sarcoma 8
Cachexia 12
At the same time, the sum of points from 0 to 3 is estimated as the probability of HIV infection is very small, 4-11 points - the disease is likely, and 12 or more - very likely.
In general, the clinical diagnosis of HIV infection is, first of all, the diagnosis of the spectrum of AIDS-associated pathology in a patient with secondary immunodeficiency. Since HIV-indicator diseases include 23 nosological forms, a syndromic approach to diagnosis is most appropriate. Almost always, the patient has a syndrome of general intoxication (unmotivated weakness, lethargy, fatigue) that develops against the background of prolonged low-grade fever or fever of unknown origin, more often at night and in the morning, accompanied by profuse sweat. The syndrome of unmotivated generalized peripheral lymphadenopathy is permanent, in 20% it is accompanied by hepatosplenomegaly of varying severity. One of the leading syndromes of the disease is the syndrome of broncho-pulmonary pathology, although deep lesions of the lung tissue in the form of pneumocystis pneumonia develop in advanced cases of the disease, because pneumocystosis develops against the background of deep immunodeficiency. But lasting more than 1 month, the syndrome of unmotivated diarrhea refers to early appearing, it is characterized by resistance to drug therapy. One of the syndromes of HIV infection is undulating arthralgia of unknown etiology. The most characteristic manifestations of the disease include the syndrome of lesions of the skin and mucous membranes, manifested by a nonspecific maculopapular rash, eczema resistant to steroid therapy, and staphylococcal impetigo. Dermatological manifestations also include recurrent fungal (mycosis, candidiasis, bacterial (folliculitis, furunculosis, hydroadenitis), viral (herpes) lesions of the skin and mucous membranes. Finally, HIV infection is also characterized by neoplasms, mainly in the form of Kaposi's sarcoma and lymphoma, and as well as some other types of tumors.
The presence in a patient of at least two clinical and two clinical laboratory (leuko-lyphoneutropenia, hypogammaglobulinemia) of the above symptoms allows diagnosing HIV infection with a high degree of confidence. But at the same time, in case of detection of two of such syndromes that are very common in patients, such as fever and lymphadenopathy, which persist for a month or more, persistent unmotivated diarrhea, weight loss by more than 10%, or profuse night sweats, give rise to staging diagnosis and thorough laboratory examination.
IN stage 2a the disease can be suspected only by the symptom of persistent generalized lymphadenopathy in a patient at risk or in the presence of an epidemiological history.
IN stage 2b(early or mild), somatic well-being, normal activity is still preserved. Lesions of the skin and mucous membranes are not severe, recurrent infections of the respiratory tract are not generalized, weight loss does not exceed 10%.
According to WHO recommendations, reliable clinical diagnosis of HIV infection in adults and children is possible in the presence of one of the 12 AIDS-indicating diseases: 1) candidiasis of the esophagus, trachea, bronchi, lungs; 2) extrapulmonary cryptococcosis; 3) cryptosporidiosis with diarrhea for more than one month; 4) cytomegalovirus damage to any organ (with the exception of and in addition to the liver, spleen and lymph nodes in a patient older than 1 month); 5) infection caused by the herpes simplex virus, persisting for more than 1 month in a patient older than 1 month; 6) Kaposi's sarcoma in a patient younger than 60 years; 7) brain lymphoma in a patient younger than 60 years; 8) lymphocytic interstitial pneumonia in a child under 13 years of age, 9) disseminated infection caused by bacteria of the Mycobacterium avium intracellulare or M. Kansassii group; 10) pneumocystis pneumonia; 11) progressive multifocal leukoencephalopathy; 12) toxoplasmosis of the central nervous system in patients older than 1 month. The presence of one of these diseases makes it possible to diagnose HIV infection in the absence of a serological enzyme-linked immunosorbent assay, or even when a seronegative result is obtained.
No less complex is the differentiation of the phases of the disease, i.e. staging according to clinical criteria. According to CDC experts (USA), the most objective criterion is the number of T-helper cells, and not clinical manifestations, because many of these conditions are often found in people who are not infected with HIV. In 1991, the Center determined that a diagnosis of AIDS can be made if: a) the infected person has one of 23 AIDS-related conditions or b) he is HIV-infected and has less than 200 CD4+ cells/mm.
Laboratory criteria for HIV infection.
Testing for HIV infection is primarily subject to:
2 . Persons with a clinic of candidal esophagitis, candidiasis of the bronchi and lungs, disseminated or extrapulmonary coccidiomycosis, pneumocystis pneumonia, extrapulmonary cryptococcosis, cryptosporidiosis with diarrhea for more than 1 month, cytomegalovirus lesions of internal organs except for the liver, spleen, lymph nodes in patients older than 6 months, cytomegalovirus retinitis with loss of vision, herpetic infection with multifocal ulcers lasting more than 1 month, bronchitis, pneumonia or esophagitis, recurrent herpes zoster, disseminated or extrapulmonary histoplasmosis, pulmonary or extrapulmonary tuberculosis, isosporiosis with diarrhea lasting more than 1 month, widespread or extrapulmonary MAC- infections, progressive multifocal leukoencephalopathy, toxoplasmosis of the brain, salmonella septicemia, Kaposi's sarcoma, lymphoma, lymphoid interstitial pneumonia (in children)
Currently, for the laboratory diagnosis of HIV infection, various methods for detecting HIV, HIV antigens and HIV gene material, as well as methods for detecting antibodies to HIV are used. All these methods have different efficiency, require different equipment and different levels of staff training. The results of these studies require competent interpretation.
Diagnosis of HIV infection includes 2 stages: establishing the actual fact of HIV infection and determining the stage of the disease. Determining the stage is inextricably followed by clarifying the nature of the course of the disease, and then the formation of a prognosis for this patient, as well as the choice of treatment tactics.
As you know, the diagnosis of any infectious disease is based on a comparison of epidemiological, clinical and laboratory data, and exaggeration of the value of one of the groups of these data can lead to diagnostic errors.
The reader should be warned at the outset that a common mistake in diagnosing HIV infection is to make a diagnosis based on a single laboratory test that the physician, for one reason or another, has too much confidence in. Some lab workers even take the liberty of diagnosing HIV infection without ever seeing the patient. Sometimes clinicians also trust laboratory results implicitly, which can only be useful as "individual witnesses in the final verdict" of the patient. During the 15 years that we have been observing HIV infection in Russia, we have seen dozens, if not hundreds, of cases of errors associated with the fanatical trust of some doctors in the results of a laboratory test. We can not dwell on quite often occurring "ordinary" errors that occur when sera are confused, documentation is incorrectly filled out, etc. The clinician must know the diagnostic value of a particular method. We know of a case when in St. Petersburg, as a result of the inept use of some “new” method, one “scientist” diagnosed an “HIV infection” to a completely healthy and uninfected person (whom, by the way, he had never seen), as a result of which the latter committed suicide. Another, no less outstanding "scientist" for several years argued to the leadership of one of the former Soviet republics that the population of this country was "stricken by the AIDS epidemic", since the "supersensitive" research method he developed "detects HIV infection in infected people much earlier than all other known methods." In both cases, of course, it was about the false reactions that gave their "latest methods."
A typical case of "establishing a diagnosis of HIV infection (virologically)" is described. Despite the fact that the described deceased man, aged 21, had no significant risk factors for HIV infection in the epidemiological history, there were negative blood tests for antibodies to HIV, not a single opportunistic disease typical of HIV infection was diagnosed, and a pathoanatomical diagnosis of lymphogranulomatosis with damage to the bone marrow, liver, spleen, intestinal lymph nodes”, the author of the above description (apparently, only in his own article) gives him a “posthumous diagnosis” of HIV infection. The basis for this "retrospective" diagnosis was the mention that the material from the patient "was examined by molecular hybridization using a radioactive probe and revealed the presence of HIV-1 virus-specific sequences in mononuclear cells." Apparently, the author of the article, under the strong impression of virological terminology, saw in "this example the exceptional value of virological diagnostics in comparison with serological ones, especially in young children."
As we have already noted, new diagnostic methods should be confirmed by old ones, and not vice versa. Therefore, our general recommendation to clinicians and epidemiologists is to remain skeptical of all "new techniques" until all their advantages and disadvantages are known. At present, this directly concerns polymerase chain reaction (PCR) diagnostics and other "gene diagnostic methods", with the help of which some researchers have already "discovered AIDS in Egyptian mummies" and "have already begun to detect it in rats." Recent advances only show that it will take several more years to fully adapt these techniques to the needs of medicine.
Until recently, disputes about whether it is possible to diagnose HIV infection without laboratory confirmation have not stopped. This would be the subject of serious discussion if methods for detecting antibodies to HIV were not widely available in Russia. However, we are of the opinion that it is quite possible. We observed many cases where the diagnosis of HIV infection was not in doubt from the moment of collecting an anamnesis and the first examination of the patient. It is difficult for us to recall a case where the typical lymphadenopathy in a native of Central or East Africa did not turn out to be a sure sign of HIV infection. Only in 2 young patients whom we had to consult, although they had previously received massive hormonal therapy, Kaposi's sarcoma on the head and body was not a manifestation of HIV infection.
Due to the tradition that has developed in Russia, millions of people are examined for antibodies to HIV without specific indications, and in most cases the doctor first receives the results of the study (a positive reaction to HIV antibodies) and only then sees the patient himself and can interview him.
It is quickly forgotten that laboratory data are only confirmation of clinical ones. In cases where the doctor already knows that the patient being examined has antibodies to HIV, he can easily make a mistake in making a diagnosis. So, in 1985-1989. we had to examine dozens of patients who were sent to Moscow from all over the country because of false laboratory confirmations of HIV infection. In 1987-1995 for one true positive “laboratory diagnosis”, based only on the determination of antibodies to HIV by enzyme immunoassay (ELISA), there were up to 2000-3000 false ones! All people with such a reaction used to be under dispensary observation for a long time, creating a lot of work for the staff of the centers for the prevention and control of AIDS.
In 90-95% of those infected, antibodies to HIV appear within 3 months after infection, in 5-9% - after 6 months and in 0.5-1% - at a later date. The earliest time for the detection of antibodies is 2 weeks from the moment of infection.
Of practical interest are cases when a patient is examined in the incubation period or at stage IIA of HIV infection and the amount of antibodies in his blood is still too low for detection. Nevertheless, with sufficient experience, infectious disease specialists quickly recognize these cases. So, for example, once the doctor M.A. Burchik, who worked in the box department of the Clinical Infectious Diseases Hospital No. 2 in Moscow, suspected HIV infection in a 44-year-old man who had returned from a trip to the United States, who suffered from a disease that clinically very much resembled infectious mononucleosis, and at the first examination was seronegative for HIV. M.A. Burchik rightly noted that the mature age of the patient is atypical for mononucleosis, because N.F. Filatov at one time called it "children's glandular fever", and some authors who observed it in adults also called it "the disease of students and lovers", i.e. persons of young age. A repeat test for antibodies to HIV, made after 1 week, also gave negative results. However, M.A. Burchik showed perseverance, and already in the third study, performed 1 month after the onset of clinical manifestations, antibodies to individual HIV proteins were detected, and subsequently, a “completely positive” reaction for antibodies to HIV in immune blotting. During the subsequent collection of the epidemiological history, it turned out that the patient had homosexual relationships during a trip to the United States, as a result of which he became infected with HIV.
Among the most studied and widespread is the method of detecting antibodies to HIV. Since HIV infection in most cases lasts for life, the very fact of detecting antibodies is sufficient for diagnosis. With HIV infection, unlike other infections, in most cases there is no need to use paired, i.e. taken after a certain period of time, serum.
The detection of antibodies can in principle detect more than 99% of people infected with HIV. Some difficulties are associated with the fact that antibodies to HIV are absent in the first weeks after infection, and in the terminal stage of the disease, their number may noticeably decrease. There is information about some, rather rare cases of HIV infection, when antibodies are not detected for a long time or disappear for a relatively long time.
Thus, from 1995 to 1997, 8 patients with clinical signs of HIV infection were identified in the USA and Canada, in whom repeated sera tests for the presence of antibodies gave negative results. All patients had clinical manifestations corresponding to the definition of AIDS, the level of CD4-lymphocytes was less than 0.2 10 9 /l. Tests for p24 antigen were positive, as were the results of detection of HIV RNA and DNA. The study of the sera of these patients in several test systems for the detection of antibodies showed that some of them detect the presence of antibodies to HIV, while others do not. Immunoblotting of sera in 4 out of 8 patients revealed the presence of antibodies to HIV proteins, i. these sera could be considered questionable (non-interpretable result).
The previous observation emphasizes the need for a comprehensive assessment of the results of the examination in the diagnosis of HIV infection, since in all cases the disease was suspected on the basis of clinical manifestations. In a number of patients from this group, a history of sexual relations with persons who subsequently became ill with AIDS could be identified. The epidemiological significance of such cases is generally low, as they occur infrequently, but theoretically they can play a role in the occurrence of individual outbreaks, which should be taken into account when conducting an epidemiological investigation.
Even earlier, experts expressed the opinion that the absence of antibodies to HIV 6 months after infection is extremely rare and a negative test result for antibodies to HIV within this period is most likely "a strong argument against the diagnosis of HIV infection." Described by P. Sullivan et al. "Seronegative" cases of clinically pronounced HIV infection accounted for only hundredths of a percent of the total number of AIDS patients detected in the United States during the same period of time. Theoretically, it can be assumed that with an increase in the incidence of HIV infection in Russia, the absolute number of such cases will increase and, accordingly, the role of seronegative sources in the epidemic process may increase. However, as the quality of diagnostic test systems and their ability to detect lower and lower concentrations of antibodies increase, these calculations may not be significant.
Since the terminology used in the laboratory diagnosis of HIV infection is not always clear to the practitioner, we must dwell on it in more detail.
Diagnostic test systems are called special sets of reagents for the detection of markers of HIV infection. Most often, as we noted above, they are designed to detect antibodies to HIV. Their main difference is only the method of detecting the reaction of the antibody with the HIV antigen. Test systems differ, in addition to the method of detecting an antigen-antibody reaction, in the selection of HIV antigens used, which can be obtained directly from HIV by recombinant methods or synthesized from amino acids, as well as in the selection of related reagents and design. Practitioners should not be confused by the expressions “third generation test systems”, “new generation test systems”, etc., which are most often used for advertising purposes. In fact, this only hides the use of new ingredients, although in fact the quality of the “fourth generation test system” can be significantly lower than that of the “first generation” test system. Thus, test systems using a “viral lysate” as an antigen, i.e. of the destroyed virus are referred to as the “first generation”, but in their ability to identify all infected people who have antibodies to HIV, they can surpass the “new generations”.
The qualitative characteristics of these tests are the ability to detect the maximum number of true positive sera, i.e. sera that actually contain antibodies to HIV (sensitivity of the test system), and the ability to register the minimum number of false positives, i.e. giving a false reaction with the diagnosticum, sera (specificity of the test system). If the declared sensitivity of the test is 99.9%, then this means that it detects 999 out of 1000 sera containing antibodies, and does not detect one serum. If the specificity is declared as 99.9%, then this means that the test will react as positive with one of the 1000 sera tested, which definitely do not contain antibodies to HIV.
As a rule, the real sensitivity and specificity of test systems are lower than those declared by manufacturers, and their value can be judged mainly by the results of practical application.
It is quite natural that the greatest number of sera containing antibodies to HIV are detected by those tests that contain antigenic determinants most often found in HIV-1. But in order to detect, for example, even more rare sera with antibodies to HIV-2 or HIV-1 subtype O, it is currently necessary to introduce antigenic determinants specific for these variants into the antigen set, i.e. constantly expand the set of antigenic determinants. The inability of the test system to detect both positive sera containing some antibodies leads to false-negative results, which can be caused by both insufficient sensitivity associated with the incorrect selection of the reagents used, and inadequate selection of the antigenic determinants used.
All known test systems have some limitations in their ability to detect all sera containing antibodies to HIV (in terms of sensitivity), if only because the amount of these antibodies can be very small, especially in the initial and final periods of the disease. However, in model experiments with previously known positive sera (“diagnostic panel of sera”), the sensitivity of some test systems can reach 100%, i.e. they detect all known positive sera used in this experiment. At the same time, of course, one should not forget that the persons conducting the tests may accidentally or deliberately select sera with certain features that affect the result of the test.
At the same time, false positive reactions are inherent in almost all test systems. This is due to the fact that antibodies to antigens similar to HIV antigens or to antigen contaminants may be present in the test materials. Thus, in the classical method of obtaining an HIV antigen from a lysate of virus cell cultures, fragments of lymphocytes are found in the final product, antibodies to which can cause false reactions, etc. It was noted that as the sensitivity of the test increases, there is a tendency to increase the number of false positive reactions.
In practice, false-negative and false-positive results are also added to this, arising from human errors, deterioration in the quality of test systems due to transportation and improper storage. Therefore, along with specificity and sensitivity determined in the laboratory, these parameters are sometimes determined in the so-called field conditions, i.e. in practical healthcare settings. As a rule, the specificity and sensitivity determined in the "field" conditions, due to the above reasons, are lower than laboratory ones. Even factors such as the quality of the water used to wash laboratory glassware, etc., can affect the results of using test systems.
Most often, antibodies to HIV are detected by ELISA methods. There are no fundamental differences in numerous commercial test systems for solid-phase ELISA, although they can differ significantly in sensitivity and specificity. Quite often it happens that the same sera give different results when using different test systems. In this regard, it is recognized that a positive result of a study in one test system cannot be considered an unconditionally positive result.
A number of methods have been proposed and used to test the specificity of antibody detection results. Among these methods, the most commonly used immune blotting reaction (“immunoblot” in the Western Blot modification. In this beautiful “scientific” name, “blot” is most likely translated as “blot”, and “western” as “western”, which reflects the direction of distribution this "blot" on paper from left to right, i.e. on a geographical map, this corresponds to the direction from west to east). The essence of the immune blotting method is that the enzyme-linked immunosorbent reaction is carried out not with a mixture of antigens, but with HIV antigens, previously distributed by immunophoresis into fractions located in accordance with the molecular weight on the surface of the nitrocellulose membrane. As a result, the main proteins of HIV - carriers of antigenic determinants - are distributed over the surface in the form of separate bands, which appear during the enzyme immunoassay.
The sera of patients infected with HIV-1 detect antibodies to the following main proteins and glycoproteins: to structural envelope proteins (env) - gpl60, gpl20, gp41, nuclei (gag) - pi7, p24, p55, as well as virus enzymes (pol) - p31, p51, p66. For HIV-2, antibodies to env are typical - gpl40, gpl05, gp36, gag - pl6, p25, p56, pol - p68.
Among the laboratory methods required to establish the specificity of the reaction, the detection of antibodies to HIV-1 (gp41, gpl20, gpl60) and HIV-2 (gp36, gpl05, gpl40) envelope proteins has received the greatest recognition. However, even here there are some differences between the opinions of individual research groups.
Thus, WHO considers positive sera in which antibodies to any two HIV glycoproteins are detected by immunoblotting. According to these recommendations, if there is a reaction with only one of the envelope proteins (gp 160, gp 120, gp 41) in combination with a reaction with other proteins or without it, the result is considered doubtful and a second test using a kit from a different series or another company is recommended. If after this the result remains doubtful, observation for 6 months is recommended (research after 3 months).
In our opinion, it is acceptable to interpret the results as positive even in the presence of antibodies to only one envelope protein, especially when it comes to examination in the foci of HIV infection. It is quite obvious that when it comes to the serum of a child who was in the nosocomial focus of HIV infection, or a blood recipient from a seropositive donor, or a sexual partner of an HIV-infected person, the diagnostic significance of a positive reaction increases dramatically. Here we once again would like to draw the reader's attention to the fact that the diagnosis of HIV infection is established not on the basis of the results of laboratory tests, but by comparing them with clinical and epidemiological data. Thus, it was in Elista that during the epidemiological investigation of a nosocomial outbreak, we observed about 10 cases when, in infected children, antibodies to only one env glycoprotein were initially noted in the immune blotting reaction.
The presence of a positive reaction with the p24 antigen may indicate a period of seroconversion, since antibodies to this protein sometimes appear first. In this case, it is recommended, depending on the clinical and epidemiological data, to repeat the study with a serum sample taken no earlier than 2 weeks, and this is exactly the case when paired sera are necessary in HIV infection.
Positive reactions with gag and pol proteins without a reaction with env proteins may reflect the stage of early seroconversion, and may also indicate infection with HIV-2 or a non-specific reaction. Persons with such results after testing for HIV-2 are re-examined after 3 months (within 6 months). If, after 6 months, indeterminate results are again obtained (no reaction with HIV-1 and HIV-2 env proteins), and risk factors and clinical symptoms of immunodeficiency are not identified, then a non-specific reaction of immune blotting is usually concluded. It is believed that in the case of true HIV infection, usually after several months of monitoring the spectrum of antibodies, a positive trend is determined, i.e. the appearance of antibodies to other structures of HIV, and on nitrocellulose in the reaction of immune blotting, the appearance of bands missing for diagnosis is observed. On the contrary, in the case of a false reaction, the results of immune blotting remain indeterminate or become negative, i.e. "suspicious" bands disappear.
The effectiveness of diagnosing HIV infection by detecting antibodies in the blood is reduced by the fact that antibodies to HIV may not be detected in the first months of infection or in the terminal stage of the disease, and, on the contrary, can be detected in the first months of life in uninfected children born to HIV-infected mothers.
Since children do have antibodies to HIV, in this case the reaction cannot be called a false positive. On the one hand, during the 1st year of life, maternal antibodies circulate in the blood serum of a child and, therefore, the detection of antibodies to HIV in children of the 1st year of life is not a sufficient basis for making a diagnosis of HIV infection. On the other hand, since HIV infection in the neonatal period can induce hypo- and agammaglobulinemia, the disappearance of antibodies cannot be considered sufficient grounds for removing the diagnosis of HIV infection. In this regard, children born to HIV-infected mothers should have been clinically observed for at least 36 months after birth. With the advent of new diagnostic methods, there is a tendency to reduce the observation period. The detection of HIV antigens or viral nucleotide sequences in such children may confirm the diagnosis of HIV infection at an earlier time, but the negative results of such studies do not completely reject it (see below). After the entire period of observation, the question of whether the child has HIV infection is decided on the basis of an analysis of a complex of clinical, immunological and serological data.
The disadvantage of the currently most common enzyme immunoassay systems is the need to use special equipment for evaluating the results of the reaction: spectrophotometers with accessories, which may include computers with special calculation programs, etc., which significantly increases the cost of research and makes the researcher dependent on many conditions, including special premises, electricity and water supply.
The use of the immune blotting method is severely limited by its high cost.
Immunoblotting, contrary to popular belief, is less sensitive than solid-phase ELISA. Therefore, in some countries, serological diagnosis is allowed after the detection of antibodies to HIV using several test kits for solid-phase ELISA, which differ in the composition of antigens. The effectiveness of the immune blotting method reduces the detection of a sufficiently large number of uninterpretable, or indeterminate results.
Theoretically, the method of detecting antibodies to HIV in saliva simplifies diagnostics; gives more false positives.
For "field" studies, all sorts of simplified versions of test systems for the detection of antibodies to HIV are currently offered. Their sensitivity and specificity can vary considerably.
In Russia, at present, the standard procedure for laboratory diagnosis of HIV infection is the detection of antibodies to HIV with subsequent confirmation of their specificity in immune blotting.
Detection of antibodies to HIV involves 2 steps. At the first stage, the total spectrum of antibodies to HIV antigens is detected using various tests: enzyme immunoassay, agglutination, combined, comb, membrane filtration or membrane diffusion. At the second stage, the immune blotting method is used to determine antibodies to individual proteins of the virus. In the work, it is permissible to use only test systems approved for use by the Ministry of Health of Russia. Diagnostic procedures should only be carried out in accordance with approved instructions for the use of the appropriate tests.
Blood is taken from the cubital vein into a clean, dry test tube in the amount of 3-5 ml. Newborns can take blood from the umbilical vein. The obtained material (whole blood) is not recommended to be stored for more than 12 hours at room temperature and for more than 1 day in a refrigerator at 4-8 °C, since the onset of hemolysis may affect the results of the analysis. Serum is separated by centrifugation or by stroking the blood along the wall of the test tube with a Pasteur pipette or glass rod. The separated serum is transferred into a clean (preferably sterile) test tube, vial or plastic container, and in this form it can be stored for up to 7 days at 4-8 °C. When working, you must follow the safety regulations.
Upon receipt of the first positive result, the analysis is carried out 2 more times (with the same serum and in the same test system).
If at least one more positive result is obtained (2 positive results out of 3 ELISA tests), the serum is examined in another test system to determine total antibodies to HIV.
Primarily positive serum, i.e. which gave 2 positive results in the first test system, is re-examined in the ELISA in the second (other) test system selected for confirmation.
When a positive test result is obtained and in the second test system, the serum must be analyzed in the immune blotting reaction. If a negative result is obtained in the second test system, the serum is re-examined in the third test system.
If a negative result is obtained in both the second and third test systems, a conclusion is issued that there are no antibodies to HIV.
If a positive result is obtained in the third test system, the serum should also be sent for analysis in immune blotting.
Immunoblotting results are interpreted as positive, indeterminate, and negative.
Positive (positive) are samples in which antibodies to two or three HIV glycoproteins are detected, negative (negative) - sera in which antibodies to none of the antigens (proteins) of HIV are detected. Samples that detect antibodies to one HIV glycoprotein and/or any HIV proteins are considered indeterminate (indeterminate or uninterpretable).
If an indeterminate result is obtained with antibodies to the core proteins (gag) in the immune blot with HIV-1 antigens, a test with HIV-2 antigens is performed.
Upon receipt of positive results of immune blotting, a conclusion is made about the presence of antibodies to HIV in the test material.
Upon receipt of a negative test result in immunoblotting, a conclusion is issued that there are no antibodies to HIV.
If an indeterminate result is obtained, repeated tests for antibodies to HIV are carried out after 3 months and if indeterminate results remain, after 6 months.
If, after 6 months, indeterminate results are again obtained, and the patient does not have risk factors for infection and clinical symptoms of HIV infection, the result is regarded as a false positive. In the presence of epidemiological and clinical indications, serological studies are repeated.
A feature of the serodiagnosis of HIV infection in children born to HIV-infected mothers is that both infected and uninfected children in the first 6-12 months of life have antibodies to HIV of maternal origin, which can then disappear. The criterion indicating the presence of HIV infection in a child is the detection of antibodies to HIV at the age of 18 months and older. The absence of antibodies to HIV in an 18-month-old child born to an HIV-infected mother is a criterion against the presence of HIV infection.
For the purpose of diagnostics, methods for detecting the virus, its antigens or gene material (specific nucleotide sequences) are also used.
Among HIV antigens, they most often try to detect the HIV-1 p24 protein, but this technique has not been widely used in epidemiological studies, since most of the antigen is not bound by antibodies only in the initial period of the disease and during the development of clinically pronounced immunodeficiency. In this regard, the method is of interest for identifying patients in the early stages of HIV infection and sometimes for assessing the progression of the disease (see below). The detection of this antigen in a child born to an HIV-infected mother can serve as a criterion for establishing a diagnosis of HIV infection in him. It is possible, however, that modifications of the method can be developed to expand its diagnostic application.
Isolation and identification of HIV culture is a reliable sign of HIV infection, however, this method is inaccessible, requires a long time, highly qualified performers and special equipment. Therefore, the isolation of the virus and its identification are carried out only for scientific purposes. Modern methods make it possible to isolate HIV in the vast majority of cases or even in all cases of true HIV infection, unless, of course, researchers have the appropriate skills, are persistent (make repeated attempts to isolate HIV) and have large funds that provide the opportunity to use a special virological laboratory equipped with modern technology and reagents. The latter condition, however, significantly limits the use of this approach, and it is usually used only for limited scientific purposes.
It should be remembered that the negative results of a single attempt to isolate HIV have no practical significance, since such attempts to isolate HIV are successful only in half of the cases. The report of the laboratory that HIV has been isolated is of greater diagnostic value, however, all laboratories conclude that it is HIV that has been isolated on the basis of their screening tests, and the doctor can evaluate the correctness of this test only by the degree of his confidence in this virological laboratory . We have repeatedly noted that some virologists were able to allegedly isolate HIV from materials that have nothing to do with HIV-infected people, for example, from materials obtained from patients with chickenpox or mumps, or even from healthy (more correctly, not infected with HIV) people.
A significant problem is also that the identification of the virus takes a relatively long time.
Finally, in recent years, the method of detecting HIV gene material has become very popular by methods of replication (amplification, reproduction) of specific gene sequences, often combined under the name of one of the variants of this method - “polymerase chain reaction”. As convincingly shown in a review of the literature on the development of this diagnostic method for HIV infection, the sensitivity of known PCR modifications for diagnosing HIV infection is only 98%, i.e. they detect only 98% of samples from HIV-infected individuals, which is significantly lower than when using ELISA (up to 99.9%). In other words, these modifications in 1998 were able to detect only 980 infected people out of 1000, and not 999, like ELISA. For this reason, they cannot be used as confirmatory tests either, as they will obviously produce more false negative results than immune blotting. One can only disagree with A.G. Shipulin et al., who attribute to their “favorite” reaction a specificity close to 100%, although in reality this reaction behaves in practice as too sensitive to external fluctuations and in inept hands and in insufficiently well-equipped laboratories gives a considerable amount nonspecific (false positive) results. The specificity of PCR also depends on the selection of the ingredients used in it, in particular the so-called primers, which should mimic the HIV gene sequences, but can not always be accurately selected. Poor selection can lead, in particular, to the fact that such tests can detect different HIV-1 subtypes with different success, for example, detect subtype B and not detect subtypes A and G, etc. However, the development of these methods is proceeding at a rapid pace, and it is possible that better quality sets of standard reagents will soon appear. In practice, physicians must take into account the operational characteristics of the diagnostic tests they offer, initially assuming that their practical value may be significantly lower than that declared by manufacturers.
The theoretical advantage of PCR is that it is able to detect HIV infection in the incubation and early clinical periods, when antibodies may not yet be present. However, it is not always able to detect infection in later periods. This may also be important in the future when trying to diagnose HIV infection in people receiving antiretroviral therapy, when the level of HIV in the blood is significantly reduced. The joint use of two methods - ELISA and PCR, which could be a way out of this situation, unfortunately, will make research much more expensive, especially if they are carried out on a mass scale.
At present, test systems for the detection of HIV gene material are approved for use in Russia. These test systems can give positive reactions to the presence of HIV markers in the early stages of HIV infection. While the experience of their use cannot be considered sufficiently large, we recommend adhering to the following tactics for their use. If positive test results for HIV infection are found in test systems of these types, an examination for antibodies to HIV should be carried out. If antibodies are detected, standard diagnostic tactics should be followed. If test results are positive for gene or antigenic markers of HIV and test results are negative for antibodies to HIV, tests for antibodies to HIV should be repeated after 3 and 6 months.
So far, the amplification method has been relatively successfully used only for diagnosing HIV infection in children born to HIV-infected mothers. As is known, the diagnosis of HIV infection in them is hampered by the presence of maternal antibodies to HIV in the blood in the 1st year of life, both in healthy and infected children. But here, too, the use of genetic engineering methods is of limited value. According to modern data, a positive result of determining the HIV gene material in a child in the 1st month of life really indicates HIV infection with a probability of 50-95%, and a negative result with a probability of 3-10% indicates the absence of HIV infection. Thus, it turns out that a child under 1 month of age with a positive PCR is probably infected, and a child with a negative reaction is very likely not infected. Repeated studies of the material from the child, made after 1-2 months, if their result coincides with the first, increase the accuracy of the diagnosis, but do not give absolute certainty. A positive PCR result obtained over the age of 4 months (closer to 6 months) is of greater diagnostic value, primarily because the concentration of HIV increases at this time. In our opinion, the information content of the results of this reaction in the early stages can be influenced by the route of infection of the child (in utero, perinatally, or during breastfeeding), which naturally determines the duration of infection. It is quite natural that in children who become infected through breastfeeding, the results of PCR in the first days of life are likely to be negative. Thus, it seems that the use of PCR to detect HIV infection in children is also not yet a reliable method for early diagnosis and may not be of such great use in the future. We believe that all children born to HIV-infected mothers should take preventive measures, such as HIV chemoprophylaxis, and even more so, it is necessary to cancel breastfeeding, regardless of the preliminary results of PCR. Specialists from the USA recommend the use of antiretroviral (preventive) therapy for the prevention of HIV infection in newborn children of HIV-infected mothers without special reference to the results of PCR diagnostics. It is likely that antiretroviral chemoprevention of HIV infection can affect the effectiveness of diagnostics, since, with it, the concentration of HIV can naturally decrease to an undetectable level. This means that in people receiving antiretroviral drugs to prevent infection, the final diagnosis by PCR should be carried out only after the end of the drugs.
However, PCR-type reactions have already found their place in the diagnosis of HIV infection. Now they are successfully used to predict the course of the disease and evaluate the effectiveness of therapy, to determine the quantitative indicators of the presence of HIV in biological fluids, which we will discuss in more detail in the following chapters.
With HIV infection, such nonspecific changes in laboratory parameters as a decrease in the level of CD4-lymphocytes, an increase in the percentage of CD8-lymphocytes, an increase in the level of P2-microglobulin, neopterin, an increase in the number of immunoglobulins, etc. can be observed. The detection of these signs is additional evidence in favor of the diagnosis of HIV - infections. However, these changes may be absent at certain stages of HIV infection (see below), have individual fluctuations in different patients, and occur in other diseases.
As we have already emphasized, the diagnosis of HIV infection includes 2 successive stages that have independent goals:
- 1. Establishing the actual diagnosis of HIV infection, i.e. determining the state of HIV infection.
- 2. Establishing a clinical diagnosis, i.e. determination of the stage and nature of the course of HIV infection.
Timely determination of the state of HIV infection is of great importance for anti-epidemic measures and leads to important legal and social consequences. Even at the slightest suspicion of HIV infection, it is often necessary to take some urgent measures to prevent the possible spread of HIV, for example, to exclude the transfusion of suspicious blood. When an HIV-infected person is found, he is removed from the donation, undergoes counseling, which can reduce the further spread of HIV. The epidemiological investigation carried out when it is detected makes it possible to identify routes of HIV transmission, which in some cases (for example, in nosocomial outbreaks) can be quickly interrupted. Epidemiological investigation identifies other sources of infection, as well as individuals at risk of infection.
The establishment of a clinical diagnosis is carried out in order to provide adequate medical care to the patient's condition. This assistance should include not only drug therapy, but also psychological support. The latter event also has some anti-epidemic significance.
Regardless of the purpose, the diagnosis of HIV infection is carried out through a comprehensive assessment of clinical examination data, the results of an epidemiological investigation and laboratory tests.
At the same time, in the first time after the suspicion of the presence of HIV infection, both the infectious disease specialist and the epidemiologist may simply not have enough data to make a final diagnosis. The results of all laboratory studies may be available only after a few weeks, and complete epidemiological data may never be obtained at all. Quite often, experienced professionals have doubts about the value or reliability of laboratory diagnosis of HIV infection. Sometimes a diagnostic decision has to be made even in the absence of the possibility of even a clinical examination, not to mention the possibility of a complete clinical examination.