The influence of concomitant HIV infection on the serological diagnosis of primary syphilis in southern Africa

The authors investigated the utility of both a non-treponemal (RPR) test and a treponemal (FTA-ABS) test for the diagnosis of primary syphilis during the emergence of the HIV epidemic in southern Africa. The serological tests were performed on 868 patients with genital ulcerations, seen in five centres. While primary syphilis was diagnosed by multiplex PCR in 163 cases (18.8%), the overall RPR and FTA-ABS seroprevalences were 24.3% and 51.5% respectively. The sensitivities of the RPR and FTA-ABS to detect primary syphilis were 69.3% and 89.6% respectively, while the specificities were 86.1% and 58.5% respectively. The performance characteristics of these tests were influenced negatively by concomitant HIV infection and the presence of other genital ulcer disease pathogens in lesions found to be Treponema pallidum PCR positive.