Towns JM, Leslie DE, Denham I, et al. - Researchers investigated discordant, T. pallidum (Treponema pallidum) PCR-positive, serology-negative primary syphilis cases as well as any clinical or laboratory factors related to failure to subsequently seroconvert. Using the Melbourne Sexual Health Centre electronic records, they selected serodiscordant primary syphilis cases that were T. pallidum PCR-positive and serology-negative. A total of 814 primary syphilis cases and 38 (4.7%) serodiscordant cases were included. Follow-up serology was done a median of 24 days later in 32, of which seroconversion was seen in 16 (50%), mostly (81%) within 6 weeks. There was a significant link between failure to seroconvert and treatment on day 1. Based on findings, it was inferred that development of serological markers can be avoided through earlier treatment of primary syphilis. Experts suggest the utility of T. pallidum PCR in detecting primary syphilis lesions prior to the development of serological markers as well as in improving diagnosis of early primary syphilis lesions. A proportion of primary syphilis infections will be missed if serology alone is used, and its repeated use is recommended if a diagnosis of syphilis is being considered.