[Question #5992] Follow up on Syphilis

17 months ago
Hi Dr, I had a follow up question.  I was going to get a test for syphilis but I have been on an antibiotic for the past seven days.  I know this would prevent a recent infection.  My question is if I had syphilis in the past year or so would I test negative because of the antibiotic I am taking for the past seven day or does it take time to get the antibodies out of system?  I would like to know if I have had it prior to starting antibiotics one week ago.  Would a test be negative no matter what because of the antibiotics (amor) I am taking for strep throat?  Does the AMOX change test results that quickly?

Thanks
Edward W. Hook M.D.
Edward W. Hook M.D.
17 months ago
Welcome back to the Forum.  On this occasion I will be responding to your question.  I have however reviewed your earlier interaction with Dr. Handsfield and agree with all that he said.  Like Dr. Handsfield, I believe that your risk for syphilis from the exposure you describe is infinitesimal.  With respect to the reliability of a syphilis blood test now that you are taking amoxicillin, the answer is that results would still be reliable at this time. In persons with syphilis, declines in antibody levels typically take months not days or even weeks.  Thus if you had a syphilis blood test which would have been positive two weeks ago, it would still be positive at this time. 

I hope this information is helpful.  EWH 
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17 months ago
I am nervous about prior exposure. Been on AMOX seven days. Would this specific test tell me if I was infected prior to antibiotics. Not sure if this is a good test

We offer the RPR (Rapid Plasma Reagin) antibody test for syphilis detection. This syphilis test measures both IgG and IgM antibodies in the blood. If the initial test results are positive, the lab will perform a quantitative RPR (titer) test. If necessary, it may also include a TPA confirmatory test at no additional charge.
Edward W. Hook M.D.
Edward W. Hook M.D.
17 months ago
Not sure if you missed it or not.  In the middle of my reply above I said "With respect to the reliability of a syphilis blood test now that you are taking amoxicillin, the answer is that results would still be reliable at this time."  This is the case.  7 days of therapy would get you started on treatment if you needed it but would not change your test results.  The RPR is a reliable, recommended and slowly changing test for syphilis.  The testing strategy quoted above is a recommended approach to testing for current or prior syphilis.  EWH---
17 months ago
Thank you, I understood your response. I was just curious if the tests they do after to confirm a case would come up negative and therefore report back a negative result even though screening test was positive. 

Thank you for your time and service
Edward W. Hook M.D.
Edward W. Hook M.D.
17 months ago
Thank you.  I'm glad I could help.  All of these tests do not differentiate between treated and untreated syphilis and, following treatment, take months to decline.  In fact, in some cases, there are persons for whom antibody levels do not decline despite effective, curative therapy.  You can believe any negative test results you get.

As per forum guidelines, as this is my 3rd response, this thread will now be closed without further responses. I hope that my comments have been helpful. EWH
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