window period for RPR VDRL blood test

I had a risky encounter on 08/25/05.  Exactly 8 weeks later I got the RPR blood test performed.  Those tests came back non-reactive.  My question is, are blood tests of that type reliable 8 weeks after possible exposure?  And do syphilis antibodies make themselves present post 8 weeks or is another blood test needed?   thanks for you time.  

[H. Hunter Handsfield, M.D.]

Yes, the result is reliable.  If you had caught syphilis, the RPR definitely would be positive by 8 weeks.  No more testing is needed.

You don't describe what you mean by "risky encounter".  If you and your partner both are male, or if one of you is a commercial sex worker, syphilis might be possible.  It also depends on where in the world you live.  In the US, syphilis is rare, with only about 10,000 new cases per year in the entire country (400 times less common than chlamydia), with most cases occurring in gay men.

Regards---   HHH, MD

[danfess]

Sorry I mistyped, the event was on 08/25/07.  Yes, actually it was a man(I didnt know at the time, it was a transexual), and I am a male.   It was unprotected oral (i received)that lasted for about 2 min.'s.  Thats why I'm concerned because I know its high risk for syphilis.  I'm glad my 8 week test was neg., but worried a little about the possiblity of a false negative.  IS this common in those RPR tests?  thanks again for your time, D  

[H. Hunter Handsfield, M.D.]

Although syphilis is sometimes transmitted by oral sex, anal sex is responsible for most infections in MSM.  In any case, the 8 week result is reliable, without worry about false negative results.