Syphilis Diagnostic Protocol with RPR

Rapid Plasma Reagin (RPR) (Human Gesellschaft für Biochemica und Diagnostica mbH, Wiesbaden, Germany) was performed using 100 μL of serum. All reactive RPR results were followed by serial serum dilutions to obtain the RPR titer. Participants who were a) positive by either TPHA or ELISA, and b) non-reactive by RPR were considered as no active syphilis. Those with positive TPHA or ELISA and reactive RPR results were also considered as having no active syphilis if RPR titers had a fourfold decrease compared to a previous test, or if they had received syphilis treatment within the last 6 months. Those with positive TPHA or ELISA and reactive RPR results were considered as having active syphilis if signs of primary (chancre on genitals, oral cavity, or perianal region) or secondary syphilis (rash, condyloma lata or mucous patches) were present or if they had a fourfold increase in RPR titers compared to previous results. Serofast status was inferred for those subjects without a fourfold decrease in RPR titers six months after treatment [6 (link)].