New Syphilis Question

Dr.,

I figured I would pay another 15 bucks to get your opinion on the latest in my sypilis saga.  As I explained in a previous post, my girlfriend had an RPR with a titer of 1:1 and I an FTA and TIA positive confirmatory tests.  I am positive that I am her only risk factor as I have been promiscuous.  I recently tested negative on the RPR screen.  However, the health department has been in contact with both of us, and they seem fairly persistent and suggested that I have a confirmatory test.  Neither one of us have ever had symptoms and she is diabetic.  I have 3 questions:

1)Do I really need a confirmatory test?  
2)How unlikely would it be that I could have syphilis and have a negative RPR (I understand the test is very sensitive).
3) I had a rocephin shot about a month before the RPR so could this have any impact on the negative result?

Thanks so much.

[Edward W Hook, MD]

You got me this time.  I think having a confirmatory test is not a bad idea.  It will help to eliminate some of the possibilities that DR. Handsfield mentioned during the last exchange.  If you had syphilis in the past and it had resolved, with or without treatment, it is quite likely that you would still have a reactive confirmatory test.   If it is negative, it greatly increases that probability, assuming that all you have said before is correct, that your GF indeed does have false positive test results on both her screening and confirmatory tests - this occurs in about 1 out of every 10,000 people.  As for your questions:

1.  Sure, what's to lose. Information is power and this is clearly on your mind.
2.  Very unlikely other than the rare scenarios you've already mentioned.
3.  A single shot of ceftriaxone would not be expected to reliably cure syphilis.  EWH

[littlenervous714]

Thanks Doctor, but you left me with some uncertainty.  The question that I am most concerned with is: What are the chances that I have latent syphilis and had a negative RPR screen?  Keep in mind the Rocephin injection and I also had strep throat treatment with either doxycilin of amoxycilin somewhat recently.  Could this make my RPR a false negative??  What kind of odds am I looking at that I actually have syphils given the false test.  I won't ask another question, I promise.

Thanks again

[H. Hunter Handsfield, M.D.]

Dr. Hook advised me of your new question and invited me to comment.  I agree with his reply above.

I suspect Dr. Hook would agree with me that although the ceftriaxone would not reliably cure latent syphilis, it probably could contribute to a negative RPR test.  However, 4 weeks is a bit too fast for that effect; i.e., it's possible but I doubt it is the explanation.  As I said at the end of the previous thread, you need to face the strong possibility that you will never have definitive answers, especially if your own syphilis confirmatory test is negative here.

HHH, MD

[Edward W Hook, MD]

Agreed.  EWH