DNA PCR or antibody

[ashhb]

I had a single unprotected encounter with a woman who I know is very promiscuous.  I understand that the odds are that I did not contract HIV but I plan to get tested anyway to relieve my anxiety.  I am married and I'm having trouble getting past the outside possibility of infection.  I plan to get tested on Friday which will be 27 days post exposure and I'm unsure whether to get a DNA PCRor simply get an antibody test.  I've read all about the pros and cons of each such as the DNA PCR is not approved, has high false positives and is costly (which isn't an issue) and that the antibody is only 85-90% accuate at this point.  My questions would be:

1. What is my actual risk.

2. Should I get the DNA PCR test now (for greater accuracy), or rely on the 85-90% accuracy of the antibody test.  I do plan to get tested again at 6-8 weeks but can't wait that long.

Thanks in advance.

[H. Hunter Handsfield, M.D.]

As I said above and innumerable other times on this forum, a 6-8 week test is conclusive for low risk exposures like this one.  In your case, you don't need any further testing at all; 4 weeks is plenty.  Even though some experts recommend a final test at 3 months, it simply isn't necessary.  But it's up to you.  I suggest you not waste your own money (or your insurance company's or the clinic's):  have only one more test, whenever you have it.

[ashhb]

Thanks again doctor.  I couldn't find a clinic or lab close by that offered a duo test so I had an antibody test at 4 weeks which came back negative.  I am much more relaxed about the situation but I will have another antibody test at 8 weeks, just to be sure.  Would you consider a negative test at 4 weeks and another at 8 to be "conclusive" or would you advise another at 12 weeks.  Thanks again.

[H. Hunter Handsfield, M.D.]

Lots of clinics and labs offer the duo test.  Keep asking.  It is routinely available at the nation's two largest lab systems, LabCorp and Quest.  You could try their websites.  Any clinic or doctor can send specimens to either of them.

[ashhb]

Sorry doctor but one last question.  Where should I look for the duo/combo test.  When I talked to the local clinic it isn't available and searching online didn't turn up anything other than descriptions of the test.  Thanks again.

[ashhb]

Thanks doctor.  I will look into the duo/combo test but will likely just get an antibody test now and if my anxiety persists again at 6-8 weeks.  I keep telling myself that the likihood is so remote that I should just move on but I think I need some type of verification in order to go forward.  Thanks again.

[H. Hunter Handsfield, M.D.]

Welcome to the HIV forum.

Odds a "very promiscuous" woman (in the US or other industrialized country) has HIV around 1 in 1,000.  Chance of transmission, if she had it, during a single episode of unprotected vaginal sex around 1 in 2,000.  That makes the chance you have HIV somewhere around 1 in 2 million (0.001 x 0.0005 = 0.00000005).  That's a low enough risk that most experts would agree you don't need testing at all, but I understand your desire to do that anyway.  The reliability of a negative antibody test at 4 weeks is 90-95%.  If we assume 90% is the accurate value, a negative result will reduce the chance you have HIV to 1 in 20 million.  That is low enough to be considered zero by anybody.  If you want still greater security, have a Duo or Combo test, i.e. one of the tests that looks for both HIV antibody and p24 antigen, a measure of the virus itself.  A negative duo/combo test at 4 weeks is 100% reliable.  I recommend against a PCR test in this situation.  Or just have a second antibody-only test at 6-8 weeks.

In the meantime, don't lose any sleep over this.  There is no realistic chance you caught HIV.

Regards--  HHH, MD