A lot of A-po ask me, my little four so low? Have I been infected for a long time?
From a clinical point of view, CD4+ count can not fully reflect the length of infection, because each person's immunity indicators are not the same, with individualized differences, in general, the northerners will be higher than the southerners, and from the perspective of the epidemic of AIDS in China, the overall disease development process in China is relatively fast, the primary four fell below 350 for about 3-5 years, while European countries may be about 5 years.
So can we have a rough idea of when we got infected? One way to roughly calculate this is the absence of bands on our confirmed report.
Because at present, China uses the Western blot (WB) method for antibody confirmation.
What is a confirmatory test for HIV antibodies?
Western blot test (WB), as a confirmatory test for HIV antibody detection, is currently the preferred method for HIV antibody confirmation in China, which can identify or affirm the results of screening tests.
WB method as the "gold standard" for HIV antibody detection is familiar to everyone, proficient in its experimental principles and methods, accurate interpretation of the immunological indications of each band type, combined with comprehensive analysis of epidemiological data, the WB band type prompt content is not limited to the conclusion of HIV antibody positivity, but also includes the source of infection, transmission route tracking and important information of clinical differential diagnosis.
How is HIV infection diagnosed?
According to the current detection strategy of the mainland, the diagnosis of HIV infection is mainly divided into two parts: screening and confirmation test, and screening is divided into initial screening and re-examination. Usually, the sample is first screened and if positive, a retest is performed; Confirmatory tests are performed on samples that are responsive to screening. The Westernmblot (WB) method is commonly used for confirmation analysis.
What are the methods of screening tests?
The following methods are commonly used for the initial screening of HIV infection.
(1) Enzyme-linked immunosorbent assay: blood, saliva, and urine samples can be used. HV antigen antibody combination detection reagent can simultaneously detect HIV antigens in the blood. Add the sample to be tested and the enzyme-labeled HIV antigen or antibody, add the substrate to color, and use the array
(2) Chemiluminescence or immunofluorescence test Light or fluorescent substrates, both antibodies can be detected, and antigen antibodies can be detected in combination. Add the sample to be tested or the HIV antigen or antibody of the fluorescent interstitial, add the luminescent or fluorescent substrate, and determine the results with a luminescence or fluorescence meter.
(3) Rapid testing and other testing tests: simple and fast, suitable for emergency testing, outpatient emergency testing. Results can generally be obtained within 10 to 30 minutes, which is conducive to more people participating in VCT services. However, the RAPID HIV detection method also has certain limitations: there is a certain false positive reaction, which must be re-examined and confirmed; There is a certain false-negative reaction; Reagents are not detected in every batch; Results cannot be preserved for a long time; It is not easy to carry out quality control. Common rapid detection methods include gelatin particle agglutination test, immunodiafiltration test, immunochromatography test, etc.
How can I determine whether I have tested positive for HIV?
The kits produced by different manufacturers will vary in the determination of results, so the determination of positive results should first be determined in strict accordance with the operating instructions of the kit used, and the following positive judgment criteria can also be referred to:
(1) In the three bands of anti-P24, anti-gp41 and anti-gpl60 / 120, at least two or more positives appear; It is based on standards adopted by the Center for Disease Control and Prevention (CDC) in 1989.
(2) WB results that cannot be judged as negative or positive can be defined as "indeterminate". It is characterized by a response band on the membrane that is associated with a known HIV protein or other unknown protein (possibly a non-viral protein), but is not sufficient to determine positive. Patients with "indeterminate" results should be retested immediately if they have clinical symptoms or a high-risk exposure history to HV, or if they remain "inconclusive," the viral nucleic acid can be measured or retested within a few months.
How to look at the problem of inconsistent antibody results
Antibody responses to HIV antigens vary from individual to individual, with some people may respond strongly to the P24 antigen and others may respond strongly to gp160, but most infected people will respond to antibodies to all the antigen components of the virus. The sensitivity of the initial screening reagents used and the coverage of antigens are also important factors affecting the test results, the antibody concentration is low in the early stage of infection, before and after the antibody yang turn, and when the patients in advanced stages have extreme immunodeficiency, and the detection of low concentrations of antibodies with reagents with low sensitivity will have a weak response, or even false negative results.
What changes in serology after HIV infection? How can I tell how long I've been infected?
After the body is infected with HIV, it will produce specific antibodies against the main antigens of HIV, such as antibodies against PI7, P24, P31, gp41, P51, P55, P66, gp120, gp160. The responsiveness of different antigens to HIV is related to the process of infection, there are also certain individual differences, and whether the antibody can be detected in time is related to the reagent used.
The time at which the antibody is produced depends on the reactivity of the host and the characteristics of the virus. As the infection progresses, the body's concentration and titer will gradually increase, and the antibody test will also turn from negative to positive, a process also known as seroconversion. Antibodies against different antigen components do not appear at the same time, Gag egg (P24, P55) antibodies usually appear earliest, and antibodies against Env (gp41, gp120, gp160) and Pol (P66, P51, P31) proteins may appear at the same time or later, P24 antigen antibodies may decline with the progression of the disease or bind to P24 antigen to form an antigen antibody complex, gp41 antibodies are stable and long-lasting, It is the main antibody detected by HIV antibody preliminary screening experiments.
Therefore, from the absence of certain bands, combined with the time of your own high-risk behavior, you can roughly determine when you were infected.