Syphilis is a complex multistage sexually transmitted infection (STI) caused by the bacterium Treponema pallidum subspecies pallidum. Syphilis transmission may be minimized by shortening the time between infection and diagnosis for which new diagnostic tools are needed. The aim of this study was to evaluate the value of Treponema pallidum Transcription Mediated Amplification (TP-TMA) assay to test mucosal orifices in addition to routine diagnostics, to increase the sensitivity of early stage syphilis detection.
Methods
Between September 14th 2021 and August 1st 2022, all participants of the national PrEP program at the sexual health center (SHC) in Amsterdam were included when visiting the SHC for the quarterly STI screening visits and in between visits. Anal, pharyngeal, vaginal and urine samples collected in Aptima tubes for Chlamydiatrachomatis (CT) and Neisseria gonorrhoeae (NG) screening, were additionally tested with the TP-TMA assay based on the 23S rRNA of TP.
Results
In total, there were 9974 SHC visits from 3283 clients included and 191 early infectious syphilis cases diagnosed; 26 (14%) primary syphilis, 54 (29%) secondary syphilis and 111 (58%) early latent syphilis. At least one sample was positive with the TP TMA assay in addition to an early infectious syphilis diagnosis for 79 of the 191 (41%) cases. In total, 119 samples from 95 visits tested positive in the TP-TMA assay, of which 16 samples from 16 clients were discrepant positive TP-TMA cases as compared to the routine diagnostics. Of these, two clients were recently treated for a syphilis infection within a week before the visit.
Conclusion
By adding the TP-TMA assay to the routine diagnostics, 14/191 (7%) additional untreated early syphilis infections were identified among participants of the national PrEP program. The TP-TMA assay is a diagnostical tool that may be used to reduce the infectious time and thus limit the transmission of syphilis.
