Evaluation of the GeneSoC rapid quantitative PCR system for Treponema pallidum detection

The incidence of syphilis, caused by Treponema pallidum (TP), is increasing worldwide. Nucleic acid amplification tests, including quantitative PCR (qPCR), are valuable for diagnosing primary syphilis, particularly using ulcer/lesion swabs. Recent studies have also shown the promising diagnostic performance of nucleic acid amplification tests using saliva. The GeneSoC platform, a rapid qPCR system capable of completing 50 PCR cycles in 15 min, has been used for the diagnosis of infectious diseases, but has not been assessed for syphilis. This study aimed to evaluate the performance of the GeneSoC rapid qPCR assay for TP detection in clinical samples. We evaluated clinical specimens from ulcer/lesion swabs (syphilis, n = 43; non-syphilis, n = 20) and saliva (syphilis, n = 33; non-syphilis, n = 20). All syphilis samples were confirmed to be positive by conventional qPCR and stored before analysis with the GeneSoC rapid qPCR assay. The GeneSoC rapid qPCR assay had a detection limit for TP DNA of 20 copies/reaction, compared with 2 copies for the conventional qPCR assay. The results for the GeneSoC and conventional qPCR assays showed 100 % concordance for ulcer/lesion swabs. For saliva samples, the positive agreement rate was lower with crude DNA (63.6 %) but improved with purified DNA (84.8 %). The negative agreement rate was 100 % for both sample types. The GeneSoC rapid qPCR assay is a promising point-of-care test for primary syphilis using ulcer/lesion swabs. However, further optimization and validation, especially for saliva, are needed for its broader clinical use.