[Question #8370] Syphilis test

45 months ago

Dear Doctor,

I forgot to ask a question last time. It’s about syphilis. I had unprotected sex in London with a couple of sex workers about three months ago. I had syphilis blood tests on day 59 and day 101 and the results are both negative. However, I took 5 days of doxycycline, 2*100mg per day, at 20 days after the last exposure. It’s given by my GP to cure epididymitis since I had testicle comfort. But I feel stomach pain so I stopped after 5 days. I also took 14 days of Ofloxacin at the main time.

Now I read that these antibiotics could affect the tests of syphilis. My question is: Are my syphilis tests 100% conclusive?

Thanks very much!

Edward W. Hook M.D.

45 months ago

On this occasion, I'll be answering your question. I have reviewed your earlier interaction with Dr. Handsfield and agree with all that he said. FYI, the risk of getting syphilis from an encounter with a CSW is very, very low. Syphilis blood tests provided conclusive results at 4-6 weeks following exposure. Thus your 59 and 101 day results prove that you did not acquire syphilis from your exposure of concern. Ofloxacin has no effect whatsoever on the syphilis bacteria and the doxycycline you took would not change the reliability of your test results. Be confident that you did not acquire syphilis (or HIV as per Dr. Handfield's earlier statements) from the exposure you described. EWH---

45 months ago

Dear Dr. Hook,

Thanks very much for your help! I have two follow-up questions:

1. In the NHS clinical guidelines for syphilis, I find the following statement:

If initial serology is inconclusive and there is a clinical suspicion, arrange repeat serology a week later and ideally at 6 weeks and 3 months. Avoid the use of antibiotics if possible at this stage if the diagnosis remains uncertain and the patient reports no exposure to syphilis. Treatment at this stage may prevent a serological response. Likewise, if the patient is requiring antibiotics for another reason then this may affect syphilis serology.

What does this mean? Will the doxycycline I took affect the syphilis test I took because it's like a 'partial treatment'? Could you please elaborate?

2. I am dating a girl now and I want to make sure I will not infect her before we have sex. I have no other exposure since the last one I mentioned. Is it 100% safe to have unprotected sex with her now?

3. Since I have no other exposures, am I 100% clear of HIV and syphilis?

Thanks again for your great work on this forum.

Edward W. Hook M.D.

45 months ago

I’m afraid you are over reading and overreacting this. I’m sorry you were having so much trouble excepting the advice the doctors Handsfield and I have provided to you. Brief answers will follow

1. Even by the conservative standards of the national health service that you site, your tests are negative and should be believed. The course of doxycycline taking 20 days after your exposure would not appreciably affect these results. As I’ve already told you, ofloxacin has no activity against the bacteria that causes Syphilis.

2. Yes

3. Yes

I hope these replies will help you to move on. EWH

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45 months ago

Sorry for my anxiety-driven question and this will be my last one. I will take my last opportunity to reassure I am 100% clear.

Can I ask what do you mean by “not appreciably affect these results”? What is “not appreciably” in terms of real-time? How many days would that be? Is it possible to measure such effects? I do want to make sure a 100% safe rather than over 99%? What’s your suggestion?

Edward W. Hook M.D.

45 months ago

Sigh. You really need to relax. “No appreciable effect” = “no meaningful effect” = “no effect”

End of thread. Please don’t worry. EWH

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