[Question #3942] Testing accuracy

34 months ago
Hello again Drs.,

I previously posted here regarding my risk during a sexual encounter with a CSW in South East Asia. You advised me the encounter was low/no risk but I recently submitted to testing anyway. I tested negative to Syphilis, Hep B, C, Gonorrhea, Chlamydia and HIV 1/2 at the 6 week (45 day to to be precise) mark with a HIV antibody/antigen assay test using a Siemans Centaur. Would the results from this encounter be conclusive? Under the HIV test one it mentions the 12 week window period. Is that just being cautious or are the results from this test reliable / accurate at this point?  

Thank you.
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
34 months ago
Welcome back to the forum. Thanks for your question.

I reviewed your discussion last month with Dr. Hook and agree with all he said. And your test results indeed are conclusive. Although some resources, including public health departments and even some HIV/AIDS experts, continue to recommend 12 weeks for conclusive testing, that advice is outdated. For over 10 years, the standard tests in routine use, including all HIV antigen-antibody tests, are conclusive any time 6 or more weeks after the last possible exposure. Your negative result proves you were not infected. No further testing is needed.

I hope this information is helpful. Let me know if anything isn't clear.

HHH, MD
---
34 months ago
Ok, so the results of the antibody/antigen test at 6 weeks are conclusive? What is the minimum time for these kinds of tests to be conclusive just for future reference? I have seen some sexual health clinics say 28 days, does that sound right? 

All the other tests were also negative, include the gon. and chlamydia urine tests. Are these results also reliable?
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
34 months ago
28 days indeed was considered conclusive, based on the known biology of HIV infection, development of antigen detectable in the blood, and the production of antibodies. In theory, all infected persons should have positive AgAb tests by 28 days. However, a review and recommendations by CDC about a year ago reported a few cases in which up to 6 weeks (actually, 45 days) was required for positive results. In fact, 28 days might still be conclusive:  it is possible that some persons tested in the various data bases gave false information (knowingly or unknowingly) about when they were exposed, such as not admitting a more recent same-sex exposure or not knowing his or her main partner was at risk. Perhaps others took anti-HIV treatment after exposure but did not reveal it. In almost all cases, 28 days is sufficient for conclusive results, but to be safe and conservative, it is best to assume that in rare cases it may require up to 6 weeks.

Your other results also are completely reliable.
---
34 months ago
This is going to sound stupid, but if I tested at 44 days this would not be considered 'conclusive'? I know this is splitting hairs but I just want to be sure as my test was right on the cusp of the 45 day period (and the exposure happened at night while the test was done early afternoon). Would it still be conclusive in your opinion with this considered? 

Anyways, it sounds like the tests are reliable and conclusive based on your advice so I think I can put this one to bed.
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
34 months ago
Yes, conclusive. There is no statistical difference between 6 weeks (42 days) and 45 days. Don't worry about it.

That concludes this thread. Let's make it your last one about this exposure, its risks, testing, etc. I do hope the discussion has been helpful.
---