[Question #10981] Antibiotics and False Negative Syphilis Test
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18 months ago
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Hello- I have read though this site and really value your expertise!
I had unprotected sex and am worried about syphilis. I have read on this forum that antibiotics can affect the reliability of RPR test results.
I have tested negative for syphilis at 7 weeks and 9.5 weeks since exposure. I completed 2 rounds of antibiotics at 4 weeks and 6 weeks (doxy only for 1 week so not likely to cure syphilis)
1. How do antibiotics with sensitivity to syphilis effect the reliability of RPR test?
2. Should I get tested anymore?
3. Should I utilize reverse testing strategy if tested again?
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Edward W. Hook M.D.
18 months ago
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Welcome to our Forum. Thanks for your questions Before I address your specific questions, let me provide some background information. Of STIs, syphilis is among the rarer. Most people do not have syphilis. You do not provide much detail about your reason for concern but following an encounter that a person feels may be risky, STIs such as gonorrhea or chlamydia are far more common. Further, at this time, most syphilis occurs among men who have sex with other men. If your partner was not another man, this too makes your risk for syphilis low. Finally the idea that antibiotics may cause a falsely negative test for syphilis is incorrect- antibiotics may delay test positivity but they do not cause falsely negative results. In response to your specific questions:
1. How do antibiotics with sensitivity to syphilis effect the reliability of RPR test?
See above. Your negative tests for syphilis at four weeks would be unlikely to effect your blood test results. A week of doxycycline would cure many cases of syphilis isf the disease was present. More importantly, given the information you have provided, you can be confident that you did not get syphilis from the encounter than you are concerned about.
2. Should I get tested anymore?
No, there is no need for additional testing. Your tests prove that you did not be syphilis
3. Should I utilize reverse testing strategy if tested again?
See above. No need for additional testing. EWH
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18 months ago
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Thank you! So is there any chance that the rounds of antibiotics could have delayed the test positivity beyond 9.5 weeks? Or is that just not possible and you have never seen this in practice?
know you already addressed this but I need to be 100 percent sure. Thank you!
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Edward W. Hook M.D.
18 months ago
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This is a repetitive question. Repeating the question is not going to change the answer. I have already told you that your tests prove that you do not have syphilis. There is no reason to worry about the antibiotics you took.
I do research and write textbook chapters on Syphilis. If you choose to not believe me, that’s up to you. My answer is not going to change. EWH.
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18 months ago
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Thank you for your trusted feedback! I completely trust your advice and value your expertise.
I have one last question for educational purposes since I have a science background:
-when do antibiotics delay test positivity for syphilis tests? Is this when testing is done early after exposure? Is this when testing is done while antibiotics are being given?
I am not worried about my case anymore. For educational purposes, it would be great to understand when and how antibiotics can delay test positivity for syphilis.
Thank you and I realize this is my last question!
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Edward W. Hook M.D.
18 months ago
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The idea that antibiotics can delay development of a positive test for syphilis is an overstatement. It is quite uncommon. The idea behind it is that antibiotics might slow the growth of the syphilis bacteria and, in that way, delay development of the anti-syphilis antibodies that are detected by the test. When persons take antibiotics soon after being exposed to an infected partner, it is far more likely that the infection would be prevented entirely.
The presence of antibiotics have no effect whatsoever on the performance of syphilis tests.
This completes this thread. Take care. EWH
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