Yes I have looked on line to understand the biology used in the testing proses but I think it would be help full if the Health nurse could explain to every one the different test and how they determine if a person is HIV positive or has AIDS and the errors that can occur
Hi the old maxx50
I will go through the current tests that we use to test for HIV.
For routine HIV screening we use a 3rd generation anti-HIV-1&2 EIA (Enzyme immunoassay) test. This is a HIV antibody test.
If this test is non-reactive (negative), no further testing is done.
If this test is reactive or equivocal, confirmatory tests including a supplemental EIA screening test (4th generation test), Western Blot (a different type of antibody test) and HIV- 1 RNA test (HIV-1 Quantitative NAT,(looks for the actual HIV virus)) are performed to confirm or rule out HIV infection.
I am not sure what you mean by “errors that can occur” but I will take it to mean the possibility that the test shows positive when you are HIV negative and the chance the test shows negative when you are HIV positive.
HIV test shows positive when you are HIV negative:
Since a large percentage of HIV blood tests are from people at low risk for HIV infection, a falsely reactive screening test can occur. We estimate that approximately 0.5% of all HIV screening tests or about 5 individuals per 1000 persons screened are falsely reactive. Falsely reactive screening test results can occur due to non-specific interfering antibodies in the blood sample. This is when we do the confirmatory HIV testing to see if it is a real infection. In some cases people will need to do a repeat test in a few weeks, this can cause a lot of anxiety for people, but luckily does not happen often.
Given this it is possible that many people on PERB had a reactive result on their first HIV screening test but confirmatory testing showed they are negative. Usually when you get your HIV result they just tell you the final result rather than what each test showed.
The reason this happens is because they make the anti-HIV-1&2 EIA test really sensitive. They don’t want someone to be HIV positive and have a negative result.
HIV test shows negative when you are HIV positive:
The most common reason for this to happen is if someone gets a HIV test before they are out of the window period.
The window period is defined as the time after HIV infection by which a given test becomes positive. The estimated average window periods for the various tests are as follows.
HIV – 1&2 EIA Screening test (3rd generation)
3-4 weeks
HIV- 1&2 EIA Screening test (4th generation)
2-3 weeks
HIV Western Blot
4-6 weeks
HIV- 1 RNA
1-2 weeks
People whose HIV screening test is non-reactive (negative) at least 3 months after the last exposure are generally considered to be uninfected.
Let me know if you would like me to clarify any point.
HN
www.healthnurse.wordpress.com
www.stiresource.com
www.bccdc.ca
