Syphilis, caused by Treponema pallidum ssp. pallidum (TPA), is a persisting global health problem. Although syphilis diagnostics relies mainly on serology, serological tests have some limitations, and it is recommended that the final diagnosis be supported by additional tests. The purpose of this study was to analyze the relationship between serology and PCR in syphilis diagnostics. From the year 2004 to May 2019, a total of 941 samples were taken from 833 patients suspected of having syphilis, in Czech Republic. In all these samples, both nested PCR detection of TPA and serology testing were performed. Of the 941 samples, 126 were seronegative, 651 were seropositive, and 164 were serodiscrepant. Among seronegative samples (n = 126), 11 were PCR-positive (8.7%). Among seropositive samples (n = 651; i.e., samples positive for both non-treponemal and treponemal serology tests), 368 samples were PCR-positive (56.5%). The remaining 164 serodiscrepant samples included RPR negative and treponemal serological test-positive samples (n = 154) and a set of 10 RPR-positive samples negative in treponemal serological tests. While the first group revealed 73 PCR-positive samples (47.4%), the second revealed 5 PCR positive samples (50.0%). PCR detection rates were highest in primary syphilis, with lower rates in the secondary and undetermined syphilis stages. As shown here, the nested PCR can improve diagnostics of syphilis, especially in seronegative patients and in patients with discrepant serology.

Department of Biology Faculty of Medicine Masaryk University Brno Czech Republic

Department of Dermatology 1st Faculty of Medicine Charles University Prague Prague Czech Republic

Department of Dermatovenerology 2nd Faculty of Medicine Charles University Prague Prague Czech Republic

Department of Dermatovenerology Faculty Hospital Brno Brno Czech Republic

Department of Medical Microbiology Faculty of Medicine St Anne's Hospital and Masaryk University Brno Czech Republic

Institute of Medical Biochemistry and Laboratory Diagnostics of the General University Hospital and of The 1st Faculty of Medicine of Charles University Prague Prague Czech Republic

National Reference Laboratory for Diagnostics of the Syphilis National Institute for Public Health Prague Czech Republic

Outpatient STI Clinic Medicentrum Prague Czech Republic

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