[Question #2463] HIV Testing, specifically 4th gen rapid testing

46 months ago
Hey Doctors, thanks for taking the time to read my post.  I am concerned about the change in the status of 4th generation hiv testing, specifically the 4th gen hiv-1/2 Ag/Ab Alere Determine rapid test widely available in the United States.  

After reading some of the posts on this board it appears that perhaps some changes in testing recommendations are occurring because of recently completed research focused on various hiv tests and this research will be published in the next several months.  

I am wondering about the status of the 4th gen hiv-1/2 Ag/Ab Alere Determine rapid test.  To me, this Alere test appears to be the most common 4th gen rapid test in the U.S. and many recommended for years that a conclusive result occurs at 28 or more days for this test.  

Is this test no longer conclusive at 4 weeks and if not when is this test now considered conclusive in terms of weeks?  For instance, is the 4th gen hiv-1/2 Ag/Ab Alere Determine rapid test now conclusive at 6 weeks instead of 4 weeks?


H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
46 months ago
Welcome to the forum. Thanks for your question.

First, almost all 4th generation tests should be considered conclusive after 6 weeks, not 4 weeks. We used to say 4 weeks on this forum, but recent data suggest that a very small proportion of infected patients may require 6 weeks for conclusvie results, so that is now our advice on this forum.

Second, recent analysis of the Alere Determine® rapid test suggests that the p24 antigen component of the test is not reliable. In effect, it functions more like a 3rd generation test rather than 4th generation. However, in real world testing this may not make much difference. The third gen tests are virtually 100% reliable 6 or more weeks after the last possible exposure.

Our advice on this forum is that people concerned about a particular exposure should a) see an expert, i.e. not rely on self testing, such as by an online testing service; and b) have a lab-based 4th generation test, not a rapid test like Determine®. However, if Determine® is done, consider it highly reliable at 4 weeks and conclusive at 6 weeks or more after exposure.

I hope this info is helpful. Let me know if anything isn't clear. Best wishes and stay safe!

HHH, MD

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46 months ago
Thanks for the response! To give you an idea where I am coming from...my wife is an RN working in home health hospice and traditional home health care settings.  She had a droplet and blood exposure (in her eyes and mouth, long story!).  This occurred a number of weeks ago.  Her work didn't know how to handle a situation like this (yeah I know kind of nuts they have no real protocol in place) and sent her to the emergency department for what I assume is baseline testing.  The patient is homebound and at this point we know that he does have hep C.  We have easy access to the Alere Determine 4th generation rapid test hence the interest in this test.  For work reasons, we're temporarily relocated to an area with not much medical care hence the Alere Determine 4th gen.  When this exposure started I saw that this board was suggesting 28 days for 4th gen but noticed that the recommendation changed based on new research so I figured I would ask to be safe.
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
45 months ago
Thanks for the epxlanation. The chance your wfie caught HIV or any other blood borne virus (e.g. hep C) from the kind of exposure you describe is exceedingly low. It is surprising she was unable to get professional advice -- all medical institutions and practices are supposed to have infection control experts available, either direclty or by contract with nearby institutions (for example, a small private practice may use the infection control services of a nearby hospital). She might still invetigate such options.

Anyway, if she and you continue to manage this issue on your own, the Determine test is fine as long as you wait until 6+ weeks after her exposure for a conclusive result. However, I'm not an expert in hepatitis C testing -- you're on your own on that one. (However, I believe that 6 weeks also is fine for that aspect.)

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45 months ago
Thanks so much.  Yes, it's an eye opening experience, many home health companies in the southwest United States appear to be very unorganized amongst so many other issues.  We came from the Johns Hopkins region so the transition to here is shocking.  She plans to switch jobs to the VA in the next few months (lots of hiring right now because so many docs and nurses are leaving the VA).  

We are at the six weeks mark in two days.  So just to confirm, a 4th Gen Alere Determine rapid test is conclusive at six weeks and so are any 3rd gen rapid tests?  If so, then we can put this behind us in just two more days and move forward.  We can't get into a specialist for many weeks unless and the only other option is an ER.  The kids have picked up on our stress levels, it's been a tough time and we try not to think about it while waiting.  Thanks again, pretty awesome you folks exist!
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
45 months ago
Note I said the 3rd gen tests (and Determine) are "virtually" conclusive by 6 weeks. Since the odds are low that the patient to whose secretions your wife was exposed has HIV, 6 week testing can be considered conclusive. However, official advice often is for final testing at 3 months. Given your wife's results so far, there is almost no chance she has HIV, and you can expect continued negative results on whatever tests you do at whatever times. But if you want absolute 100% conclusion at 6 weeks, a lab based blood test is the way to go, not a rapid test like Determine.

That concludes the two follow-up comments and replies normally included with each thread. However, I'll leave this thread open a few more days in case you want my feedback after testing at 6 weeks.

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45 months ago
Thanks Dr. Handsfield,
So testing was done at six weeks.  The test was a laboratory test.  The paper doesn't say the name of the test, just that it was non-reactive.  The paperwork did have some generic wording:

"HIV 1&2 AB screen, If this 4th generation immunoassay is reactive, then there would be presumptive evidence for the presence of HIV-1 antibodies, HIV-2 antibodies, or p24 antigen."

I am hoping this is the correct test and that we are now cleared.  We called the lab for further info about the specific brand of test run and we hope to get this info soon but it sounds like they ran a 4th generation test based on this generic wording and I assume all 4th generation lab tests look for ab and ag in the blood?

All Hep lab tests were clear too.

Thanks again
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
45 months ago
There is no need to know the specific test done. The important info is that you had a 4th generation test, which is conclusive. Yes, they all check for both Ag and Ab (that's the definition of "4th generation"). Also glad to hear about negative tests for hepatitis.

That completes one more than the usual follow-up comments and replies and so concludes this thread. I hope the discussion has been helpful.

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