Vulval swabs as alternative specimens for ligase chain reaction detection of genital chlamydial infection in women

Abstract

A ligase chain reaction (LCR)-based assay was recently shown to be highly sensitive and specific for the detection of Chlamydia trachomatis not only in cervical specimens but also in first-void urine (FVU) specimens form women. The suitability of using vulval swabs as an alternative specimen that can be obtained by noninvasive means for the diagnosis of genital chlamydial infection by LCR was investigated. In a first study of 169 women, vulval, endocervical, and urethral swabs were tested by LCR, culture, and a combination of enzyme immunoassay (EIA) followed by confirmation by direct fluorescent-antibody assay (DFA), and the results were compared with those obtained by testing FVU specimens by LCR and EIA-DFA by using a specimen from an infected patient as a reference standard. Of the 169 women tested, 27 (16%) were shown to be infected. Whereas LCR showed high sensitivities with all specimen types (85.2% for vulval, urine, and endocervical specimens; 92.6% for urethral swabs), the sensitivities of culture and EIA-DFA were high only with endocervical swabs (74.1 and 70.4%, respectively), being 22.2 and 40.7%, respectively, with vulval swabs. In addition, urine testing by EIA-DFA also showed a poor sensitivity (48.1%). In order to further compare LCR performance with vulval specimens to that with FVU specimens, a second study was carried out with specimens from 312 women, of whom 26 were infected. Comparable sensitivity was obtained by LCR with vulval swabs (88.5%; 23 of 26) and FVU specimens (92.3%; 24 of 26). The results indicate that vulval swabs may serve as suitable alternative to specimens that can be obtained by noninvasive means for the detection of C. trachomatis by LCR.