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PCR Accuracy - HIV Exposure -Concerned and Confused
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PCR Accuracy - HIV Exposure -Concerned and Confused

I had a PCR and anitbody test on day 17 after potential exposre.  I have read through many threads but have not found what I was looking for.  Your help would be appreciated.

I am married with children and very concerned.  I had unprotected vaginal sex with a female sex worker in a Latin American country 29 days ago.  I read that 10% of all sex workers in that country are HIV positive.  

On day 10 after exposure I had chills, on day 11 I had a BAD sore throat and mouth that lasted until day 21, on day 19 the glands in my arms and legs became sore and last to day 21, on day 25 my sore throat became bad again and on day 28 I began to have pain in my arm pit glands again.  Even though I have had chills from time to time, I have not had a fever whenever I checked. I know you have said that symptoms are not a diagnosis, but I thought I would let you know.

I went to the doctor on day 12 and on day 19. Strep test was negative on day 12 and he could not feel any swollen glands on day 19.  He said to treat symptoms.

I have read that you do not recommend PCR due to possibility of false positives.  I have not been able to find out how much reliability you can put on a PCR test if it is done.  However, I know it is recommended to follow it up with an antibody test later.  

Both of my PCR and antibody test returned negative.  My questions are:

1.  I have read that an antibody test at 17 days is too early to rely on.  If so, why do you think that the infectios desiese Dr. (not a GP) would advise having one?

2.  How reliable is the PCR test at 17 days?  I have read that that the FDA has not approved it for diagnosis and that some do not recommend it, but I have also read that it is highly effective and some do recommend it.

3. What are the specific  statistics on the PCR test.  I have not seen this anywhere.  Most say there can be chance of false negatives.  What are the actual percentages of false negatives?

4.  It is now day 29.  Should I have another antibody test done now?  Would that combined with the earlier PCR provide enough evidence?  Or, should I wait until week 5 or 6?

5.  If I do have another antibody test, should I ask for a fourth generation test?

Your responses are very helpful to those that can not talk to others about their situation.  Thank you!




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The doctor who tested you probably can answer your questions better than I can.  But you can be close to 100% certain you don't have HIV.  If your symptoms were due to HIV, the PCR test definitely would have been positive.  The timing of that test (17 days) is less important than the fact that you had symptoms at the time it was done.  HIV cannot cause symptoms without being detectable in the blood.  I do not know the specific statistics on PCR test performance in this setting; to my knowledge it hasn't been studied carefully.

Follow your doctor's advice about when to be retested and what test to have.  My opinion is that a single antibody test (without further PCR testing) 4-6 weeks after your exposure is all you need.  Don't worry about "generation" of tests.  The difference between early and more recently developed tests is whether they are positive early, e.g. 2-3 weeks.  Once beyond 4-6 weeks, all currently avaiable tests are just as good.

Bottom line:  You don't have HIV.  Repeat testing will confirm it.  Good luck--

HHH, MD
10 Comments
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Avatar_n_tn
So, if you test negative and then shortly after experience "symptoms" that would be a better time to test? I understand that symptoms have nothing to do with/without infection, however, what if you test negative at nine weeks and have symptoms after that. Possible late seroconversion? Since he had symptoms during his test (which were negative) this is a strong indication he was not infected? Just trying to determine if a negative then "symptoms" afterward are a cause for concern.
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Avatar_n_tn
Dr.,

Don't mean to hijack the thread but I posted a follow up in a previous question that was probably further back then you check.

I went to an HIV specialist and at Day 15 he ran a Quantitative ELISA, Western Blot and an Ultrasensitive RNA Viral load test (50 copies) which all came back negative.  The doctor stated that if I was indeed infected, one of the tests would have come back positive.  He stated that the virus would be going crazy by day 15 unless my antibodies had kicked in and then the ELISA would be positive. I also took a PCR DNA test at 15 days that was negative.

I am somewhat reassured but still paranoid and freakin out about this.  Do you agree that one of the tests would have come back positive at 15 days if I was infected?  Do I need to test further?
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Avatar_n_tn
You have a doc who is an HIV specialist, which I am not; he probably knows more than I do.  Follow his advice.

When I don't respond to a follow up quesiton, it is because I choose not to.  No follow-up comments in this thread jump.

HHH, MD
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Avatar_n_tn
Back to the response to the original question, I have read on this site so many times about probabilities and time to positive and the small difference in tests. But I just wonder where does the data come from when estimating 90% by 4 weeks, 95% by 6 weeks, ...etc. Do you go by trials of different tests that are done by labs like the following?

http://www.zeptometrix.com/hivseroconversion.htm

Or is it just based on personal experience?
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239123_tn?1267651214
The same question has been asked and answered several times and I don't have time to repeat the several paragraphs it would take.  In brief, it's mostly a combination of the opinions of experts plus the biology of the tests; plus a small amount of data in animal models, which don't always translate to humans.  To get more accurate information would require studying hundreds of persons, known for sure to be infected (not just exposed) at a particular time, then tested daily for up to 3 months.  That research will never be done--much too difficult and expensive, and unnecessary except for the occasional worried/anxious person.  Although people like that are a dime a dozen on this forum, they are a small minority of all people tested for HIV.

HHH, MD
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Avatar_n_tn
thanks. Besides all the HIV information, I have learned a lot from this forum by reading your levelheaded approach to problems and professional style.
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Avatar_n_tn
Doctor,
I understand you didn't answer my question for several reasons. I am trying to post a question and pay but I keep getting an error message as follows. I want to pay the $ and get an answer but the same thing keeps showing up....see below.

Warning
Referring URL does not match accepted URLs.
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239123_tn?1267651214
I can't help.  Use the "contact" link to communicate with MedHelp administration.
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A related discussion, Please help my queri was started.
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A related discussion, RNA and PCR accurracy was started.
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