Hi there. I read your history with interest. Yes it is possible to get a positive TPHA & a negative RPR (VDRL
). However, like i stressed on another public forum query, this has to be interpreted with caution & taking the individual case history & clinical features in consideration.
To begin with, the VDRL can be negative simply because of the antigenic load. This can be confirmed by doing the test in 'high dilutions'. Also, it may turn up false negative. It is not a very 'sensitive' test..in that it may detect a lot more than it excludes but based on this, a definitive treatment cannot be made. Very commonly long standing fevers etc can easily manifest as VDRL positive & then one is in a quandry. What it does supply when positive is a guide (albeit not always reliable) to progress of treatment.
The TPHA test too can manifest with both false positivity or negativty. I understand this must be all confusing for the ordinary person &believe me even dermatologists' & immunologists consider this an 'academic graveyard'!
In your case, the best advice i can give you is stick with your dermatologist/venereologist on the ground. When in doubt, a TPI test is mre relevant (treponema pallidum
immobilization test) &/or a FTA-Abs test (immunoflorescent treponema antibodies
if this facility available near you at a large centre). If none available, i would recommend using the age-old tried & trusted 28 day regime of a safe Erythromycin
tabs to treat as for secondary syphilis
(given your time frame & h/o multiple exposures). I find erythropmycin both a safe & effective alternative to penicillin mainly because of something known as the Jarisch Herxheimer reaction
which believe me is something you dont want to take a risk with...& the details are too long to go into on a public forum!
Trust all your questions stand answered & wish you a quick recovery & safe health..& Please do practice Safe Sex
..whatever the variety you should choose to indulge in. Cheers & Good Luck!
Dr Praveen Rodrigues MD
Dermatologist, Cosmetologist, Venereologist
Vikram Hospital, Bangalore, India.