[Question #7101] Clarification on HIV testing results

9 months ago
Hi Docs, will keep it as brief as possible:
I’m a heterosexual male, HIV negative as of Dec 31st 2018. Timeline since then as follows...

- Jan 1st 2019: I performed  x unprotected cunnilingus on white New Zealand girl of unknown status, but unlikely intravenous drug user.  NO anal or vaginal intercourse
- Jan 3rd 2019 (36 hr later): PEP commenced (Truvada 2 drug regime). Against the advice of STI clinic admittedly 
- Jan 25th 2019: HIV test = negative
- Jan 29th 2019: PEP finished
- June 6th 2019 (4 months PEP completion): slightly REACTIVE  Elisa (1.05 index). Clinic thinks false positive but runs Western  Blot = NEGATIVE. Clinic says I DON’T have HIV
- Feb 1  2020 (12 months post PEP completion) no further exposure risks. Due to anxiety I retest. Elisa slightly REACTIVE  again, Western Blot NEGATIVE again. Told I’m negative.

My questions:
- Am I conclusively negative? Reason I’m struggling to move on (apart from my anxiety) is because prior to Jan 19 I’d never recorded a false positive on Elisa before...
- Assuming  the answer to previous question is ‘yes’, what are some reasons why I’m now recording reactive Elisas?

Added note: I’ve started therapy for my HIV anxiety. 
Edward W. Hook M.D.
Edward W. Hook M.D.
9 months ago
Welcome to our forum and thanks for your question. I’ll be glad to comment.  Let’s start with the exposure that you described. If you had come to see me on January 2, 2019 asking to receive PEP, I would not have been willing to prescribe it. Performance of cunnilingus, if even if your partner did have HIV, is a virtually no risk sex act.  There are no known instances in which HIV has been acquired from performance of kind of cunnilingus. The chances that you are the first Person to acquire HIV in this way are minuscule.  I would also add that PEP is typically given for a period of one month, not four.

Now, a comment on your test results. I am unsure why in this day and age you are being tested with a combination of in ELISA testing followed by a Western blot. These testing methods are out of date.  Currently recommended tests for HIV are the fourth generation, combination HIV antigen – antibody tests.  A second comment is that characterization of an ELISA test result as “slightly” reactive is does not make sense to me. Like pregnancy either the test is positive or not.  Irrespective, negative Western blot tests on two occasions more nine months apart indicate that you do not have HIV and should not be concerned.

In summary, I am quite confident that you did not acquire HIV from the exposure you described. The exposure was a virtually no risk event, you took postexposure prophylaxis which was not needed, and you have multiple negative test results. I would not be concerned in the least. If you wish to test further, at this point any future testing should be performed using modern combination antigen/antibody tests. Personally I feel no reason for further testing. 

I hope that my comments are helpful to you. EWH
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9 months ago
Thanks for the prompt reply Doctor. Clarifications from my end as follows:
- PEP was for 28 days. My first reactive HIV test was taken 4 months after finishing PEP (5 months after cunnilingus). 2nd set of tests undertaken 12 months after finishing PEP. 
- re: the tests -  I’m based in Australia and test was undertaken here. My understanding was that the  Elisa here is a 4th generation antibody/antigen test? The ‘slightly reactive’ was in relation to the signal cut-off. Cut-off being 1, my result being 1.05 or thereabouts. Having said that I’ll ask my doc should I retest again...

The Western Blot is undertaken as a confirmatory year here, and is only run if the Elisa comes back as reactive, as in my case.  Both Western Blots (5 and 12 months post cunnilingus) were negative. 

With the above in mind, does this change your assessment at all, that is, am I conclusively negative?
Edward W. Hook M.D.
Edward W. Hook M.D.
9 months ago
Thank you for the clarification. The testing protocols used in Australia are state of the art and your results should be believed. A small proportion of persons without HIV do have falsely positive HIV ELISA tests. The fact that your index values were so low are also consistent with your results being falsely positive. At this point, and following your clarifications, I am quite comfortable in assuring you that your tests prove that you did not acquire HIV from the events in January 2019 that you describe. 

I see no reason for further testing. 

Thanks again for your clarifications. I hope my further comments are helpful EWH
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9 months ago
Great, thanks Doctor, definitely puts my mind at ease.

Seeing as I get 3 posts, I may as well use them! 

In your opinion is there any  risk the 28 day course of PEP  resulted in a false negative on the Western Blots taken 5 and 12 months after PEP completion? I guess I have a residual concern for two reasons; The first is me being ask to believe the results of  one type of test (negative Western Blot) over another (positive Elisa), and the second is that prior to the cunnilingus I’d never reported a false positive on tests before....

If WB’s are more accurate, why aren’t they used from the outset?

Thanks 
Edward W. Hook M.D.
Edward W. Hook M.D.
9 months ago
I am saddened that you are having difficulty excepting your test results. The reason the ElLISA tests are used first is because they are much faster and easier to perform.  This makes testing much more efficient and readily available. The ELISA tests also have occasional of falsely positive test results. A person who is infected with HIV would have both a positive ELISA and a positive Western blot test.  Falsely positive results in ELISA tests vary from manufacturer to manufacturer Because different manufacturers use different components in putting together their tests. Falsely positive tests may BE transient or long-standing. Your test results however clearly indicate that the low positive ELISA test you mentioned above was a falsely positive test result.

There would be absolutely no residual effect of the PEP you took five or 12 months following completion. Your test results are valid.

I hope this information is helpful in clarifying things and helping to resolve your uncertainty. EWH
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