RPR 1/2 TPHA going up

Question

Hello, I has syphilis 3 year ago and was treated with 2 extencyclin shots. last year my VDRL was 1/2 and TPHA 640. This year VDRL is 1/2 but TPHA is 1280. I had no sex at for the last 2 years. What could be the problem ? Problem the TPHA test or bad treatment ? THanks.

Answer

There is no difference in those THPA results, as that is only a 2-fold increase in titer. If there is reinfection or reactivation, we expect a 4-fold or greater increase in the titer. The VDRL or TPHA can remain positive for months to years after successful treatment.