Abstract
BackgroundSyphilis is a growing public health problem among men who have sex with men (MSM) globally. Rapid and accurate detection of syphilis is vital to ensure patients and their contacts receive timely treatment and reduce ongoing transmission.MethodsWe evaluated a PCR assay for the diagnosis of Treponema pallidum using swabs of suspected early syphilis lesions in longitudinally assessed MSM.ResultsWe tested 260 MSM for T pallidum by PCR on 288 occasions: 77 (26.7%) had early syphilis that was serologically confirmed at baseline or within six weeks, and 211 (73.3%) remained seronegative for syphilis. Of 55 men with primary syphilis, 49 were PCR positive, giving a sensitivity of 89.1% (95% CI: 77.8%-95.9%) and a specificity of 99.1% (95% CI: 96.5%-99.9%). Of 22 men with secondary syphilis, 11 were PCR positive, giving a sensitivity of 50% (95% CI: 28.2%-71.8%) and a specificity of 100% (95% CI: 66.4%-71.8%). Of the 77 syphilis cases, 43 (56%) were HIV positive and the sensitivity and specificity of the PCR test did not vary by HIV status. The PCR test was able to detect up to five (10%) primary infections that were initially seronegative, including one HIV positive man with delayed seroconversion to syphilis (72 to 140 days) and one HIV positive man who did not seroconvert to syphilis over 14 months follow-up. Both men had been treated for syphilis within a week of the PCR test.ConclusionsT pallidum PCR is a potentially powerful tool for the early diagnosis of primary syphilis, particularly where a serological response has yet to develop.
Highlights
Syphilis is a growing public health problem among men who have sex with men (MSM) globally
Performance of PCR against serology – broader definition Using the broader case definition, 77 (26.7%) of the 288 PCR specimens were collected from men with primary or secondary syphilis at baseline and 211 (73.3%) were collected from men without syphilis
Of the 55 men with primary syphilis, 49 were PCR positive, yielding a sensitivity of 89.1% and a specificity of 99.1%
Summary
Syphilis is a growing public health problem among men who have sex with men (MSM) globally. Rapid and accurate detection of syphilis is vital to ensure patients and their contacts receive timely treatment and reduce ongoing transmission. Australian men who have sex with men (MSM) with HIV infection are disproportionately affected by syphilis. Only ~10% of Australian MSM have HIV infection they contribute around half of all cases of infectious syphilis among MSM [3,4]. Community-based cohort studies have shown that the incidence of syphilis in MSM with HIV infection is 5–10 times higher than in MSM without HIV [5]. Reasons for Syphilis is at its most infectious in its primary and secondary stages, so early detection has been modelled to have the maximum benefit for preventing its onward transmission [8]. The interpretation of syphilis serology can be problematic in primary syphilis because serological responses might be delayed, often requiring the patient to return for re-testing
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