Aims Co-infection with HIV has been shown to alter the serological response to, and the course of, infection with Treponema pallidum. We aimed to determine whether the rate or magnitude of response to treatment, as measured by falling Rapid Plasma Reagin (RPR) titres, was different in HIV positive compared to HIV negative patients in the modern era.
Methods A retrospective case note review was undertaken of patients who were diagnosed with syphilis between 1 January and 31 December 2008. The change in RPR titre at 1, 3, 6 and 12 months post-treatment was determined. Statistical analysis was performed using Microsoft excel; p values were calculated using χ2 or Student t test.
Results During the study period, 57 HIV negative and 23 HIV positive patients were diagnosed with syphilis. Of the patients with a RPR titre greater than neat at diagnosis, 30/40 (75%) HIV negative patients and 12/15 (80%) HIV positive patients showed a two dilution or greater fall in RPR titre 3 months following treatment (p=0.72), with 36/39 (92%) and 16/16 (100%) achieving a two dilution drop by 6 months, respectively (p=0.24). There was no significant difference in the median RPR titre at diagnosis between HIV positive and negative patients at all stages of syphilis infection. 3/16 (19%) HIV positive patients and 3/38 (8%) HIV negative patients, who were not thought to have been reinfected, continued to have a RPR titre of 1:16 or greater at 6 months post treatment (p=0.26). Where data were available, all these patients achieved a RPR titre of less than 1:16 by 12 months post treatment. Two patients, both HIV positive, were re-infected during the study period, one patient being re-infected twice.
Conclusions Overall, treatment appeared to be effective and the majority of patients showed a two dilution or greater fall in RPR by 6 months post-treatment. There was no significant difference in the rate or magnitude of response in HIV positive compared to HIV negative patients.