Use of PCR in the diagnosis of early syphilis in the United Kingdom.

OBJECTIVES: To evaluate a Treponema pallidum polymerase chain reaction (PCR) test in the laboratory diagnosis of early syphilis in the United Kingdom. SUBJECTS AND
SETTING: Men and women attending genitourinary medicine clinics in England.
METHODS: A trial PCR service was offered for the analysis of swabs of ano-genital or oral ulcers suspected to be syphilitic in origin. Clinical details, results of treponemal serology, and other relevant laboratory tests carried out by the sending laboratories were obtained retrospectively by questionnaire.
RESULTS: Data from 98 patients, representing 100 episodes of ulceration, were analysed. The majority of patients (70) attended clinics in the Greater Manchester area. Eighty six patients were male and 58 were men who have sex with men (MSM), of whom 24 were HIV positive. PCR results agreed with the clinical diagnosis for 95 patients; samples from 26 patients were PCR positive and serologically diagnosed as primary (18) or secondary (8) syphilis, whereas 70 patients had PCR negative samples and were not diagnosed as having active syphilis. These data include two HIV positive patients who were PCR positive 12 and 21 days before their treponemal seroconversion. One positive PCR result was not supported by positive treponemal serology (this patient coincidentally received a 10 day course of co-amoxiclav 1 week after sampling). Three patients had negative PCR results but positive syphilis serology. The sensitivity, specificity, positive and negative predictive value for primary syphilis were 94.7%, 98.6%, 94.7%, and 98.6%, respectively, and for secondary syphilis these were 80.0%, 98.6%, 88.9%, and 97.2%, respectively.
CONCLUSION: PCR is a sensitive and specific test for T pallidum, and an important adjunct to dark ground microscopy and treponemal serology in diagnosing infectious syphilis in the United Kingdom.