[Question #9323] Hiv test “rapid” vs “lab-based”

33 months ago

Hi Doctors,

I (37, male, live in UK if that matters) would like to ask about the following exposure:

Vaginal sex (no condom) and oral sex (no condom, both ways) with in total 6 sex workers during a business trip to London and Paris in August, 2021.

I initially had the following negative HIV tests:

A rapid finger prick test at 4 weeks (don’t know what type), results in 20 minutes

A test with blood from vein(arm) at 4 weeks(again, don’t know what type), results back in 2 days

A fourth generation test at almost 6 weeks(40/41 days) with blood from vein(arm), results back in 2 days

A fourth generation test with blood from vein(arm) at 8 weeks, results back a few hours later

A test with blood from vein(arm) at 3 months (again, don’t know what type, I think it’s fourth generation but I am not sure), results back in two days

I was relaxed until very recently I had swollen lymph nodes and testicle pain a few weeks ago. Went to a doctor and was given some antibiotics then I recovered. But this reminded me about the exposures with sex workers last year and made me anxious again.

So I went to a clinic and had a fourth generation test with blood from arm at 13 months after exposure. Results came back the next day, negative.

However, I searched a lot online and became very anxious: although I had fourth generation tests with blood from arm, I am not sure if the tests I had were indeed “lab-based”. I don’t know what kind of machine or brand they use. And I read some where online that some labs/clinics can perform so-called point of care(rapid) tests on blood from vein(arm) as well. I fear that what I had were actually rapid fourth generation tests. I just really don’t know and can’t verify. So I would like to have some assurance from you:

Is it possible that a fourth generation test performed in a laboratory is not really “lab-based”but a “point of care”test?
Let’s assume all fourth generation tests I had were rapid(point of care) ones, are they still conclusive?
Are rapid(point of care) fourth generation tests as accurate as “lab-based” ones?
When does a rapid(point of care) fourth generation test give conclusive results after exposure, no matter how high the risk was?
Can I be 100% sure that I am HIV free?

I really appreciate your help!

33 months ago

To add: I am uncircumcised if that matters. If you need more details about my exposure, please let me know!

Edward W. Hook M.D.

33 months ago

Welcome to the Forum and thanks for your questions. I'll be glad to comment. Let me start with the bottom line- your testing proves without a doubt that you did NOT acquire HIV during the encounters you describe. Further testing is unnecessary and would be a waste of time and resources. Let's now address your specific questions and I'll add a comment about your symptoms:

Is it possible that a fourth generation test performed in a laboratory is not really “lab-based”but a “point of care”test?

HIV testing terminology can be confusing. The term "4th generation" refers to any tests that test for the presence of both HIV antigen (the virus protein) and antibodies to the HIV (a reflection of the infected person fighting the virus). These tests come in different formats - some are "rapid" and can be done at the point or care or in a lab, others are totally lab based and require specialized machinery. They perform equally well, i.e. they are equivalent for detection of infection in every way. In some settings where a rapid answer is needed or the volume of testing is low, the point of care tests may be done rather than invest in the complex and expensive machinery needed to perform lab-based tests. On the other hand, the "lab-based" tests are more cost-efficient for testing substantial numbers of specimens. Thus it really does not matter which format of test was used for your test(s). The results are reliable and prove that you do not have HIV

2. Let’s assume all fourth generation tests I had were rapid(point of care) ones, are they still conclusive

yes, see above.

3. Are rapid(point of care) fourth generation tests as accurate as “lab-based” ones?

Yes

4. When does a rapid(point of care) fourth generation test give conclusive results after exposure, no matter how high the risk was?

Results of 4th generation tests, irrespective of format, are conclusive at 6 weeks following an encounter

5. Can I be 100% sure that I am HIV free?

Yes

Hope this helps. EWH

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33 months ago

Thanks for your crystal clear reply Dr Hook!

I wanted to add that I am uncircumcised but I think based on your answers the risk at the time doesn’t matter given my test results. I am totally HIV free now, am I correct?

And you mentioned you will add a comment on my symptoms?

33 months ago

And I have one more follow up question: Regarding the blood samples took from my arm, does it matter if my test(point of care or “lab-based”) was performed on whole blood or plasma or serum? Are there any differences in terms of accuracy?

Thanks for you patience!

Edward W. Hook M.D.

33 months ago

Circumcision status somewhat increases the risk of infection if exposed but has no impact on the accuracy of testing. You can be confident in your test results. You do not have HIV.

Testicular discomfort is not a symptom of HIV. As for lymph node swelling, this is a non-specific reaction to inflammation. Most people have lymph nodes which can be felt if one searchs carefully and assessment of swollen lymph nodes should be performed by a trained clinician. Further, it sounds like your lymph node swelling is better or has resolved ("until very recently I had swollen lymph nodes...") and the swollen lymph nodes associate with HIV do not go away.

EWH

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Edward W. Hook M.D.

33 months ago

We provide up to three responses to each client's questions. This will be my final response, following which the thread will be closed without further responses.

No, these tests are accurate irrespective of the sort of specimen used.

I urge you to accept that you were not infected by HIV, accept the results and move forward.

End of thread. EWH

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33 months ago

Thanks! Your advice is very helpful. I will move forward.

Have a great day!

Edward W. Hook M.D.

33 months ago

Thank you. EWH---