Detection of genitourinary tract Chlamydia trachomatis infection in pregnant women by ligase chain reaction assay

Abstract

Objective: To compare the sensitivity and specificity of a ligase chain reaction assay of cervical swabs and voided urine with those of cervical swab tissue culture for the detection of genitourinary tract infection with Chlamydia trachomatis in pregnant women.

Methods: Infection with C trachomatis was assessed in cervical swabs by culture and in both cervical swabs and voided urine specimens by a ligase chain reaction assay specific for C trachomatis plasmid DNA. The matched cervical swab and voided urine specimens were collected from 462 women during routine visits to prenatal clinics. Standard criteria that defined infection included: 1) a positive cervical culture result or 2) a negative culture but a positive ligase chain reaction result in either the urine or cervical specimen that was confirmed by supplementary testing. Test performance was assessed by determination of sensitivity and specificity, and differences in paired results were determined using McNemar analysis.

Results: The prevalence of genitourinary C trachomatis infection was 6.1% (n = 28) by cervical culture (sensitivity 30.1%; specificity 100%), 18.2% (n = 84) by ligase chain reaction of cervical swabs (sensitivity 90.3%; specificity 100%), and 16.9% (n = 78) by ligase chain reaction of urine (sensitivity 83.9%; specificity 99.5%). Relative to the number of women with a positive culture or a confirmed ligase chain reaction-positive cervical swab, the sensitivity and specificity were 82.8% and 97.9%, respectively, for ligase chain reaction of urine and 96.6% and 100%, respectively, for ligase chain reaction of cervical swabs. Ligase chain reaction of cervical swabs and urine detected 89.3% and 82.1%, respectively, of women with a positive cervical culture.

Conclusions: Ligase chain reaction assay of cervical or urine specimens detected considerably more pregnant women with C trachomatis infection of the genitourinary tract than did cervical culture. Ligase chain reaction testing of urine is a simple and effective means of screening pregnant women for genitourinary tract infection with C trachomatis.