To evaluate the performance of a new improved enzyme immunoassay (EIA) kit for the detection of Chlamydia trachomatis in vaginal swab and endocervical swab specimens from female commercial sex workers, in comparison with a conventional EIA test and a polymerase chain reaction (PCR) assay.
A high risk group of 163 female commercial sex workers who visited a sexually transmitted disease (STD) clinic in order to undergo screening for major STDs, including chlamydial infection, were enrolled. A total of four swab specimens, including two vaginal and two endocervical specimens, were collected from each woman by a clinician. To identify C trachomatis, a new improved EIA kit (IDEIA PCE), a conventional EIA kit (IDEIA), and PCR assay (Amplicor) were used. Discrepancies in the results were resolved using supplementary PCR assay. A female patient was considered to be infected with C trachomatis if the IDEIA PCE test and PCR test for both sample sites (endocervical and vaginal) gave positive results. Following resolution of these discrepancies, relative sensitivity and specificity, confidence intervals, and predictive values for each type of specimen by each assay were calculated.
Of the 163 women tested, 35 (21.5%) were shown to be infected with C trachomatis. The relative sensitivities in vaginal swab specimens were 88.8%, 68.6%, and 91.4% using IDEIA PCE, IDEIA, and PCR, respectively. The relative specificities in vaginal swab specimens were 99.2%, 99.2%, and 100%, respectively. The relative sensitivities in endocervical swab specimens were 85.7%, 77.1%, and 91.4% with IDEIA PCE, IDEIA, and PCR, respectively. The relative specificities in endocervical swab specimens were all 100%.
The results obtained in this study suggest that the sensitivity and specificity of IDEIA PCE test on vaginal swab and endocervical swab specimens were similar to those of PCR assay on the two types of specimen. It is concluded that IDEIA PCE test on vaginal swab specimens is an acceptable, sensitive, and less invasive approach for the detection of C trachomatis in commercial sex workers with a high prevalence of C trachomatis infection.