Objectives: To investigate the contribution of a real-time polymerase chain reaction (PCR) assay for the detection of Treponema pallidum in various biological specimens with the secondary objective to compare its value according to HIV status.
Methods: Prospective cohort of incident syphilis cases from three Swiss hospitals (Geneva and Bern University Hospitals, Outpatient Clinic for Dermatology of Triemli, Zurich) diagnosed between January 2006 and September 2008. A case-control study was nested into the cohort. Biological specimens (blood, lesion swab or urine) were taken at diagnosis (as clinical information) and analyzed by real-time PCR using the T pallidum 47kDa gene.
Results: 126 specimens were collected from 74 patients with primary (n=26), secondary (n=40) and latent syphilis (n=8). Among primary syphilis, sensitivity was 80% in lesion swabs, 28% in whole blood, 55% in serum, and 29% in urine, while among secondary syphilis, it was 20%, 36%, 47% and 44%, respectively. Among secondary syphilis, plasma and cerebrospinal fluid were also tested and provided a sensitivity of 100% and 50%, respectively. Global sensitivity of T pallidumby PCR (irrespective of the compartment tested) was 65% during primary, 53% during secondary, and null during latent syphilis. No difference regarding serology or PCR results was observed among HIV-infected patients. Specificity was 100%.
Conclusions: Syphilis PCR provides better sensitivity in lesion swabs from primary syphilis and displays only moderate sensitivity in blood from primary and secondary syphilis. HIV status did not modify the internal validity of PCR for the diagnosis of primary or secondary syphilis.
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