How Do I Prepare for an ELISA HIV Test?

The tests currently used as diagnostic methods include anti-HIV antibody detection, virus culture, nucleic acid detection, and antigen detection. Among them, the detection of viral antibodies is the most commonly used method. This is not only because of the specificity and sensitivity of such tests, the method is relatively simple and mature, and the more important reason is that HIV antibodies are short-lived after viral infection. The entire window of life outside the "window period" is long-term, stable and detectable. In some special cases, when antibody testing fails to meet the needs of HIV infection diagnosis, virus isolation and determination, nucleic acid detection, and antigen detection can be used as auxiliary means. This includes the diagnosis of atypical serological reaction samples, and the window of HIV infection. Early diagnosis, early neonatal diagnosis and diagnosis of special samples.

HIV-antibody detection method

(One)

Western blot test (WB), band immunoassay (LIATEK HIV III), radioimmunoprecipitation test (RIPA) and immunofluorescence test (IFA). The commonly used confirmation test method in China is WB.

(1_ Western blot (WB) is a widely used experimental method for the diagnosis of many infectious diseases. As far as the etiological diagnosis of HIV is concerned, it is the first confirmation experimental method for confirming HIV antibodies. WB test results Often used as a "gold standard" to identify the strengths and weaknesses of other methods.

Confirmation test process:

There are mixed HIV-1 / 2 types and single HIV-1 or HIV-2 types. First test with HIV-1 / 2 mixed reagents, if negative, report HIV antibody negative; if positive, report HIV-1 antibody positive; if the positive criteria are not met, judge the HIV antibody test result uncertain. If a specific indicator band of HIV-2 type appears, HIV-2 immunoblotting reagent is required to perform an antibody confirmation test for HIV-2. If it is negative, report HIV-2 antibody negative; if it is positive, report HIV- 2 The antibody is serologically positive, and the sample is sent to the national reference laboratory for nucleic acid sequence analysis.

The sensitivity of WB is generally not lower than that of the initial screening test, but its specificity is very high. This is mainly based on the separation, concentration and purification of different antigen components of HIV. It can detect antibodies against different antigen components, so WB method can be used. Identify the accuracy of the preliminary screening experiment. From the results of the WB confirmation test, despite the selection of better quality reagents, such as the third-generation ELISA, there will still be false positives in the preliminary screening test. The accurate test must be obtained through the confirmation test.

(Two) immunofluorescence experiment (IFA)

The IFA method is economical, simple, and fast. It has been recommended by the FDA for the diagnosis of WB uncertain samples. However, expensive fluorescent microscopes are required, and well-trained technicians are needed. The results of observation and interpretation are susceptible to subjective factors. The results should not be stored for a long time, and IFA should not be developed and applied in general laboratories.

HIV antibody confirmation test report

Results of HIV antibody confirmation tests are reported in Schedule 3.

(1) Meet the HIV-1 antibody positive judgment standard, report "HIV-1 antibody positive (+)", and do consultation, confidentiality and epidemic reporting after testing as required. Meet the HIV-2 antibody positive judgment standard, report "HIV-2 antibody positive (+)", and do the post-test consultation, confidentiality and epidemic report work according to regulations.

(2) Meet the HIV antibody negative criteria and report "HIV antibody negative (-)". If a "window period" infection is suspected, further HIV nucleic acid testing is recommended to make a clear diagnosis as soon as possible.

(3) Meet the criteria for the determination of HIV antibody uncertainty, report "HIV antibody uncertainty (±)", and indicate in the remarks to wait for "Retest after 4 weeks". ^[1]