Subjects first go to a nationally recognized AIDS screening laboratory (generally in provincial and municipal health and epidemic prevention stations, disease control centers, dermatosis prevention centers (hospitals), and large general hospitals) to do a screening test, and then repeat the test with two reagents, that is, re-examination (negative people do not do it).
If one or both reagents are positive after re-examination, the samples will be sent to the nationally recognized AIDS confirmation laboratory (see appendix) for confirmation testing.
After the above initial screening tests (including initial examination and re-examination) and confirmation tests, a report can only be issued if the HIV antibody is positive, and the final diagnosis can be made by combining the epidemiological history and high-risk behavior history.
In other words, the laboratory examination of AIDS is generally the first screening test 1 ~ 2 times and the confirmation test 1 time. However, some people were positive after the initial screening twice, and the test results were confirmed as "uncertain". Such people generally require a review after 3 months.
If it is confirmed that the test is still "uncertain" at the time of re-examination, there are still three months before the re-examination and the result is still "uncertain" or negative, then HIV infection can be ruled out.
Extended data:
According to the statistical normal curve model, between one standard deviation and two standard deviations (that is, between one month and two months), the number of people infected with HIV will account for 67%, 95% between two months and three months, and 99.999% above three months.
Therefore, it can be understood that if the infected person still does not produce relevant antibodies after more than 90 days, the probability is only one in a thousand, that is, one in a thousand infected people still does not produce antibodies after more than 90 days.
For the value of 90 days, the influence of the difference of several days on the probability value of 99.999% can be ignored. The probability of one thousandth of an event can be considered as a small probability event statistically.
Generally speaking, it is a screening method to detect whether there is HIV infection by detecting related antibodies.
So there is no so-called window period. However, this method is more likely to produce false positive results, and it must be done twice in a row, and both results are positive before the test report can be issued.
References:
Health News Network-How to Determine the HIV Window Period
References:
Health News Network-China AIDS testing window shortened to less than 2 weeks.