Hi there. At the outset, serological tests for syphilis
are a touch tricky to interpret. This will require the help of a qualified dermatologist
on the ground togehter with assesment of the sexual history & clinical features.There are a lot of false positives & false negatives & each test has to be interpreted in that given clinical scenario taking into account the clinical history of sexual exposure, time since exposure & clinical features manifested. Once ascertained if the syphilis is primary, secondary or tertiary, the treatment will vary accordingly. There are different schools of thought as regards treatment with injection benzathine penicillin, or the newer derivatives eg, Azithromycin
. CDC has certain guidelines for the treatment of syphilis that can be easily accessed over the internet. However, after treatment more often than not, the VDRL
et al does not become negative for months altogether...usually anywhere from 3-6 months but i have come across cases that remain positive for longer sans any clinical manifestations.This does not mean one needs to continue treatment. I do hope i have cleared this doubt you have. The TPHA test is another matter & may never become negative. Again, like i mentioned earlier, the STS tests have to be interpreted in conjunction with the clinical features of that particular case. Cheers & Good Luck!