[Question #7152] HIV testing question for Doctors

60 months ago

Hello Doctors:

My question is about confusion regarding 4th generation ag/ab rapid tests by fingwr prick made by Alere.

I am old enough to remember when HIV testing had to be done via vein blood draw and have even found archived (4+ years old to be fair) replies here that recommend vein blood draw tests over rapid finger prick blood tests.

Last year I had an Alere rapid 4th generation test done at a planned parenthood clinic. It was negative. With no further exposures I decided to have another two weeks ago — virus fears maybe? Since i have not had any exposures in the last twelve months (much longer than that really) does my negative Alere 4th generation rapid test results mean it is impossible that i have HIV?

Is there a vein blood draw test I can take that would provide a more reliable, definitive conclusive result? Or have i taken the best possible test already for as absolute conclusiveness as possible?

Thank you

60 months ago

I should add that my test from a few weeks ago was negative as well!

Edward W. Hook M.D.

60 months ago

Welcome to the Forum and thanks for your question. I suppose it is hard to believe that you can get test results from a fingerstick specimen that are equivalent to the results of testing performed on venous blood but the fact is that the results are equally reliable. Early on after it was introduced the Alere fingerstick there were modest problems with the sensitivity of the test in detection of early HIV infections. Those problems were resolved and the analytic performance of the Alere fingerstick 4th generation is equivalent to the performance of the test performed on venous blood. FYI, the reasons for the two tests vary. The fingerstick test is quicker but takes more operator time to perform. On the other hand, the venous blood makes it easier to perform large numbers of specimens.

Given your lack of recent exposures, you can have confidence that you did not have HIV at the time of testing. You're in the clear. No need for further testing related to past exposures. EWH

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60 months ago

Thank you you are right intuitively there is a bridge I am trying to cross.

So would it be correct to assume that having a blood draw venous 4th generation lab test would be having the same test done as the Alere 4th gen fingerstick? Both tests are identical?

If so, can I then assume that the tests I have had are the current gold standard? And the idea of confirming via a third lab based 4th gen test would be a complete redundancy because it’s the same as the Alere 4th gen fingerprick test?

And lastly as asked above there is no test available that can add additional conclusiveness or better more accurate results?

Sorry to ask but this is all very confusing and anxiety inducing!

Thank you

Edward W. Hook M.D.

60 months ago

Yes. a venous blood test would be redundant for you. The tests that had do represent that current standard for testing. Believe the test results! There is no test available that is going to provide you "better" results than the tests you had. Please believe your test results. In the situation that you have described, I see no need for further testing to prove that you are not infected. EWH
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60 months ago

Thank you this is very helpful, I will use the last question hopefully in this way.

I have read that regarding lab based 4th gen tests:

In terms of sensitivity, a Centers for Disease Control and Prevention (CDC) review identified four studies of two different assays, with sensitivity always above 99.7% for established infection. A Health Protection Agency evaluation found that nine out of the ten tests they evaluated had a sensitivity of 100%, while a French evaluation found that ten of twelve tests had a sensitivity of 100%. The lowest sensitivity was 99.8%.

I have also read that the rapid Alere test I took has a sensitivity of 99.9%.

My questions are and sorry to be so scientific based but that is what your expertise if for right?

1) Does the lab based 4th gen test have 100% sensitivity and the Alere rapid only 99.9%?

2) Does this mean that the Alere rapid could be less trustworthy in terms of producing a false negative?

Personally it is hard to navigate these numbers, I was under the impression that 100% was impossible to achieve in diagnostic test I get your point that both rapid and lab based 4th gen tests meet the same standard, but if one performs better than the other?

4) Is it the case that both really have 99.9% sensitivity -- the CDC site shows Alere Finger stick whole blood99.9 (99.4-100) and and for the lab based 4th gen tests
Plasma/serumHIV-1: 100 (99.63-100). ---- what does this really mean and why do they say 99.9 vs 100 and then have ranges?

I have a wife and want to be iron clad as sure as I can possibly be and my hope is you can see the confusion and recognize it as curious and NOT argumentative in any way possible!!

Can you please make this clear to me and the forum members, thank you!

Edward W. Hook M.D.

60 months ago

The is really a statistical question which invites nervous people to quickly get into the weeds. All calculations of test performance are estimates since they don’t test everyone who could be tested. The larger the sample size, the more precise the estimate But it is still an estimate. Tests evaluated using large numbers of participants are more precise. More participants and more positives increases the calculation of sensitivity and specificity as well as reduces the size of the confidence interval around those calculations. I suspect you are getting into the weeds.

1. No change in my original assessment. The performance of the ALERE fingerstick, when done as directed, is equivalent to lab based tests. There are no perfect tests. For all current 4th generation HIV tests taken more than six weeks after an exposure, the results should be believed.

2. See above, no.

3. Correct, there are no perfect tests.

4. See above.

I hope the information that I have provided are helpful to you. As you note as this is my third response to your questions, this thread will now be closed without further responses for me. The thread will be closed in a few hours. Take care. Please don’t worry and believe your test results. EWH

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