Detection of Chlamydia trachomatis in genitourinary medicine clinic attendees:: comparison of strand displacement amplification and the ligase chain reaction

Nucleic acid amplification (NAA) methods for the diagnosis of genital Chlamydia trachomatis infection perform well but are technically demanding. Strand displacement amplification (SDA) assay is a new NAA method that offers technical simplicity but its comparative diagnostic performance is unknown. Here, we compare the diagnostic performance of ligase chain reaction with that of SDA in first-catch urine (FCU) samples from both male and female patients and in endocervical swab (ECS) specimens. Attendees (715 men, 291 women) of a city-centre genitourinary medicine clinic were studied. FCU specimens were collected from all the men and from 205 of the women in the study. Two ECS specimens were collected from each of the women. Discordant results were resolved using an in-house nested polymerase chain reaction technique. Samples positive in two out of the three assays were considered positive. Prevalence of C. trachomatis infection was 9.2% and 9.1% in the men and women, respectively. Sensitivity, specificity, positive predictive value and negative predictive value of SDA in FCU specimens from the men were 95.5%, 100%, 100% and 99.5%. respectively. In the female group, the figures for FCU and ECS specimens were 77.3%, 100%, 100% and 97.3%, and 90.9%, 100%, 100% and 97.3%, respectively. In this high-prevalence population, SDA assay is an effective method for the detection of C. trachomatis in FCU specimens in men and in ECS (but not FCU) specimens in women. Further studies in lower prevalence populations are required.