You have become confused on your syphilis test results because of two mistakes. The first might be the lab's fault or your own:  the TPHA should not have been done. Initial testing for syphilis should ONLY include RPR; or, in some labs, an EIA IgG test. If either of these is negative, it is proved syphilis is absent and no more testing is done. TPHA (and certain other tests) are designed and only intended to confirm positive results with the initial test, so it is a mistake to select both RPR and TPHA for testing in your circumstance. (Of course if that's what the lab advises, it isn't your fault. In that case, it's likely a lab hoping to extract an unnecessary fee.)

The second mistake is in your interpretation. The borderline result of the TPHA (exactly at the cut-off between positive and negative) should be viewed as completely negative. Once you got to that point, it was not unreasonable to test once more, but the final results prove unequivocally you do not have syphilis.

The bottom line is you have experienced both unnecessary costs (I hope you didn't pay too much!) plus longer-than-necessary uncertainty and worry. Sorry you went through that. Next time you find a need to test for syphilis, have only an RPR or EIA test; leave the box unchecked for TPHA or other confirmatory test. (And by the way, with a female partner a single episode of oral sex, or even vaginal intercourse, is extremely low risk for syphilis. I really do not recommend testing for it after any single encounter unless you know for sure your partner had it.

I hope these comments are helpful. Let me know if anything isn't clear.

HHH, MD