[Question #11386] Syphilis test

Avatar photo
14 months ago

Hello doctor. Sorry for my bad English, it's not my native language. I had sex with a sex worker in central Europe in Hungary if that matters. Oral sex was unprotected, but sex with condom. After 1 week, my skin next to my scrotum ( groin area) turned red on both sides and also sweated on one side. The skin is cracked and sweated a little bit. The dermatologist said it was a fungal infection. He gave me an anti-fungal ointment. I was already worried about syphilis then. Exactly 6 weeks and 1 day (43 days) after sex, my RPR test and syphilis Igm/Igg test were negative. A few days after the test, I took antibiotics due to a dental problem, azithromycin 500mg once a day for three days. Then I read online that the syphilis test is reliable after 12 weeks. Now, exactly 5 months after the sex and 3 months after taking the last antibiotic, I repeated the test. RPR test negative Treponema Igg/Igm Clia test negative. Is it possible that this test is false negative because of the antibiotic even after all this time? Would you recommend retesting later? Or is it time for me to calm down?

Avatar photo
H. Hunter Handsfield, MD
14 months ago
Welcome. Thank you for your confidence in our services. Your English seems fine -- or you have a good translation program!

It is certain you do not have syphilis. Your sexual exposure was low risk for syphilis, the symptoms you describe are not caused by syphilis, and a dermatologist's diagnosis of fungal infection is very reliable. The rash had nothing to do with the sexual exposure you are concerned about. Most important, your negative blood tests are conclusive. Azithromycin or other antibiotics do not make syphilis blood tests falsely negative. They can make a test negative by curing the infection, but they do not merely suppress it. Your negative test results remain completely reliable even with the azithromycin.

You do not need any more syphilis tests, and it definitely is "time for [you] to calm down!"

I hope this reply is helpful. Let me know if anything isn't clear.

HHH, MD
---
---
Avatar photo
14 months ago
Thank you for your answer. I've been trying to calm down for the past few weeks. However, I read that antibiotics can delay a positive syphilis test. In my case, during the 3 months (exactly 14 weeks) between the test and taking the last antibiotic, this would definitely have happened if I had syphilis? And I also read that azithromycin has a long half-life. It is still effective in the body 2 weeks after intake. Are you sure that 5 months after sex, my test would not be negative even with antibiotics if I had syphilis? Thanks for your reply.
Avatar photo
14 months ago
Also, I believe that the negative test 6 weeks after sex, which happened before taking the antibiotic, could it not have been negative if I had contracted syphilis?
Avatar photo
H. Hunter Handsfield, MD
14 months ago
Antibiotics can make syphilis tests negative by curing the infection. But they rarely just suppress or delay positive test results. In addition, around the world -- and especially in Europe and North America -- almost all syphilis bacteria are resistant to azithromycin, which therefore can have no effect on syphilis diagnosis. Your negative result at 6 weeks is 100% reliable.---
---
---
Avatar photo
14 months ago
Thank you for your answer. There's nothing left for me to calm down. I think I only told myself about this whole syphilis thing. Logically, it is impossible that the negative test I received 5 months after sex would not have detected it if I had caught it, my immune system would have had to produce antibodies in that time, despite the antibiotic, since 3 months have passed since taking it.  Thanks again for your answers. I wish you the best.
Avatar photo
H. Hunter Handsfield, MD
14 months ago
All correct.Thanks for the thanks. I'm glad to have helped.


---