[Question #9349] Specific HIV Testing questions:

33 months ago

Greetings again from SoCal - this is my second question, and in addition, I’ll be making a donation to ASHA. Your honest, direct answers are very appreciated. I have two questions, and since I asked about my exposure previously, these are a bit more test-specific. Along with some obsessing, I’ve become somewhat fascinating with different types of HIV testing methods:

First, I’m curious if, after five weeks, there is a difference in taking a 3rd generation as opposed to a 4th generation test. I ask, because after quite a bit of reading, it seems that the p24 antigen may become undetectable after 35 days or so. If that is, indeed, the case, then is a 4th generation test more specific at picking up the antibodies, or is it the same as the 3rd generation?

My second question is this: If money isn’t an issue, where in the Los Angeles area can I get a 4th generation RAPID test? Or, how do I go about finding where? I’ve wanted to get a DETERMINE HIV-1/2 AG/AB COMBO test, but it seems that all of the testing centers in the Los Angeles area only offer the INSTI rapid test.

Thanks for taking the time to respond - these questions arise more from curiosity. But, I find it interesting that there are quite a few 4th generation rapid tests on the market, but none seem to be used in such an “HIV-dense area”. Any help would be appreciated.

Edward W. Hook M.D.

33 months ago

Welcome back to the Forum. On this occasion I'll be addressing your follow-up questions as whether Dr. Handsfield or I take any specific question is more a matter of chance than anything else. In preparing to answer your current questions I did review your recent interaction with Dr. Handsfield and agree with all that he said and, like him see little scientific reason for further testing given your negative test at 31 days. Had your symptoms been due to HIV, your earlier tests would certainly have been positive. Further, while the official recommendation is that results at 6 weeks are conclusive, neither of us has seen or heard of someone with a negative 4th generation test beyond 4 weeks who went on to become positive.

In comparing the 3rd generation, antibody only tests and the 4th generation, combination antigen/antibody tests the main advantage to the 4th generation tests is earlier detection of infection due to the fact that detectable antigen (virus) levels are present in recently infected persons before antibodies. I cannot comment on the specific, proprietary methods used for antibody detection in the various tests but I can tell you that they are similar, and most importantly, perform in statistically equivalent fashion for all tests. I would have confidence in your results no matter which 4th generation test is performed.

I cannot comment on where in LA you might get a RAPID 4th generation tests. Your local health department or a clinic focusing on HIV care may be able to provide that information. FYI, one the specimen is in the lab, testing takes just a few hours so the question you really want to look for as you seek further testing (not that I think it is needed) is what is there turn-around time until results are available to the client.

I hope this information is helpful. EWH

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33 months ago

Thanks for your response, Dr. Hook ... although the test I took at 31 days was an INSTI, not the 4th generation. In addition, I recently took a 41 day INSTI, which was also negative. That said, I do have one final testing question: Today, I mailed in an at-home test kit, where I prick my finger for blood, and put drops of blood on a spot-card (containing five spots). I did this, let the blood dry, followed directions, and sent it to the lab. From what I've read, dried blood-spot cards are just as effective as blood taken from a vein and put in a tube. Anyway, I'm just curious if my result on a 4th Gen blood-spot card at 45 days will be a result I can call conclusive. I'm assuming so, but just wanted to make sure as I await for results this next week. In addition, I was wondering if you think my 6-week (41 day, actually - one day shy of 6 weeks) INSTI negative is "close" to conclusive. Thanks in advance - it was a pleasure to donate $50 dollars to ASHA.

Edward W. Hook M.D.

33 months ago

Let me start by thanking you for your donation to ASHA. It is a great organization which does much to promote sexual health. I'm confident your donation is appreciated.

Regarding your earlier test, given the results of your INSTI test which I would consider very close to conclusive, I am confident that your next test will be negative and is entirely conclusive. When the results come back, I anticipate it will be negative and thereby prove that you were not infected with HIV. There is no need for further testing. EWH

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