My last full STD test was in October 2017. All test came back negative. I tested again on 7 February  2018. All test came back negative except for discordant syphilis result. EIA test positive, RPR test negative, TPPA test negative. I do not have further details of test eg. how many titer of RPR .I understand that based on the algorithm syphilis is unlikely. My doctor seem concerned, citing that the oral sex was quite recent and both exposure was with sex worker. She suggested I do a CIA Igm test, which I did on the 14th Feb and is now waiting for its results.

Does the fact that my previous Syphilis test was (I assumed ) a clear negative in October 2017 last year but now showing discordant result a sign of concern? How reliable is the CIA Igm test in not showing a false positive. And what would be your take of my situation. Btw, I have no symptoms. I could not find any sores on my penis with my untrained yeyes Many thanks for your help. 

Also, I am currently bad sore throat, GP gave me Augmentin tab 1GM. If i take it, will it affect the repeat test if I do it 2 to 3 weeks later. Thanks.

Welcome to our Forum.  I'll try to help.  Syphilis blood tests are troubled by false positive results and my suspicion is that is what you have experienced.  The exposures you describe are very, very low risk for any STI, including syphilis and your test results are most consistent with a falsely positive EIA test, something that can occur transiently or be a lifelong problem.  Different EIA tests use different chemistries as well so a falsely positive EIA with one test may or may not be positive in other tests, depending on the brand of test used by the lab.  OTOH, if you had syphilis, each test -EIA, RPR, TPPA and others, irrespective of manufacturer would be positive.   I think based on your initial test results. most experts would tell you that your EIA test was falsely positive and not perform further testing.

IgM tests are unlikely to solve your concern.  Both currently available EIA tests and RPR tests typically detect both IgG and IgM antibodies and IgM tests tend to have more trouble with false positive results than IgG tests. 

Let's see what your IgM test shows.  If it is negative, I would be confident that your recent test result was falsely positive.  If positive, my guess is still that it is a false positive result and would suggest repeat testing in a few weeks.  The augmentin you took should not adversely affect your test results.  EWH

I read CDC also recommened a retest if there is risk of syphilis in past 4 weeks. Based on what you said, am I right to say my activity in within the past 4 weeks (protected oral sex) would not qualify as a risk for syphilis, or too low a risk to even consider.

If I do a retest, can I expect results to be more "normal" eg. Eia negative, Rpr negative, Tppa negative? Many thanks again

Thanks for your follow-up questions.   With respect to the CDC's qualified assurance, I would say that, as a rule, the CDC seems to be qualified and conservative in their advice and recommendations.  As a governmental agency the CDC tends to be conservative in their recommendations, taking what I presume is a conservative stance in which they seem to feel that they cannot "afford" to be wrong or challenged in their advice.  Personally, I am comfortable that your results are falsely positive and that re-testing will show that. 

With respect to the issue of re-testing, I think the 4 week recommendation for retesting is longer than is needed and suspect that re-testing at two weeks would be sufficient.  If you had acquired syphilis I would expect that that your tests would all become positive while if the result is falsely positive (which I expect that it is) the results would be either unchanged or the EIA result would have become negative at the time of re-testing. 

I hope this helps.  If not, please re-state the question and I will try again.  EWH