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Test Reliability

Hello Doctors,

I won't going into the specific details of my story but bottom line is I had UNprotected vaginal sex with a CSW (i'm male, csw was female). Since then I have taken two hiv antibody tests through stdalert.com. The specific test is called HIV IgG Antibody by ICMA from Labcorp. I took one test at 4 weeks and one test at 8 weeks. Both came back as non-reactive which I assume means negative?

1. Is the specific test I mentioned above reliable?

2. Do these test results at 4 & 8 weeks mean I'm in the clear? Can I go on with my life now and not worry at all about hiv?

3. Do I need to take another test at 12 weeks(3months) and 6 months to make sure I'm absolutely negative?
1 Responses
239123 tn?1267651214
MEDICAL PROFESSIONAL
Welcome to the forum and thanks for your question.  I'll try to help.

Although you seek to deemphasize the exposure, that's usually important in judging someone's risk.  If the risk of HIV from a particular event were, say, 1 chance in 10,000, and a test is then done that (at a particular point in time) is not 100% reliable, but "only" 99%, then the chance the person caught HIV becomes 1 in a million.  Thare are acceptable odds for all but the most anxious and worried.

In your case, the chance any particular CSW in the US has HIV is typically under 1%, often under 1 in 1,000; and if she was infected, the transmission risk for a single epsiode of unprotected vaginal sex is on the order of 1 in 2,000.  Thus, even before you were tested, I would judge the chance you caught HIV as something like 1 in 200,000 to 2 million.

But now on to your specific question:  Every HIV antibody test produced in the US, approved by the US Food and Drug Administration, and used by any and all US labs is virtually 100% reliable by 8 weeks.  I don't know about this particular test, except that LabCorp is a highly respected national lab that has very high standards.  Obviously, it is in their interest to use the most accurate tests available!

Those comments address questions 1 and 2.  As for 3, the fact is that the antibody tests are probably 100% reliable by 8 weeks, even though the manufacturers' official advice (and CDC's advice) is that 3 months is required for a definitive result.  (Six months is for sure not necessary; that's old news left over from tests that haven't been in use for 15 years or more.)  If you are interested, here is a link to a thread that discusses why official advice remains 3 months even though 6-8 weeks is adequate:

http://www.medhelp.org/posts/show/1347755

In summary, the chance you caught HIV started out very low; and the test results you have had prove you didn't catch HIV.  All is well and you don't need any further testing.

Best wishes--  HHH, MD
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