Sensitivity of the ligase chain reaction assay for detecting Chlamydia trachomatis in vaginal swabs from women who are infected at other sites

Objective: To assess the sensitivity of the ligase chain reaction (LCR) assay for Chlamydia trachomatis in vaginal swabs from women who were positive in cervical samples and/or urines. Subjects: 413 women attending the genitourinary medicine clinic, St Mary's Hospital, Paddington. Methods: The LCR assay was used to test vaginal swabs from 46 women who were C trachomatis positive at one or both of the other sites by direct fluorescent antibody (DFA) staining, by an enzyme immunoassay (EIA), or by the LCR assay. Results: The LCR assay of vaginal swabs had the following sensitivity values using confirmed positive results: 93% (41/44) compared with DFA staining of cervical deposits, 93% (41/44) compared with the LCR assay of cervical samples, 93% (28/30) compared with an EIA for cervical samples, 91% (39/43) compared with DFA staining of urine deposits, and 93% (39/42) compared with the LCR assay of urine. Four women had vaginal swab samples negative by the LCR assay; one was positive only in the urine and two had cervical samples containing a small number of chlamydial elementary bodies. Conclusion: Testing vaginal swabs by the LCR assay is a sensitive method of detecting chlamydial infection; the results suggest that this procedure could be used as an alternative to examining urines in a screening programme for chlamydial infection in the community.