Comparative performance of the Roche COBAS Amplicor assay and an in-house real-time PCR assay for diagnosis of Chlamydia trachomatis infection.

This study investigated the comparative performance of the Amplicor assay and an in-house semi-automated, multiplex real-time PCR for the diagnosis of genital chlamydial infection. Four different assays, the COBAS Amplicor CT test (Amplicor PCR), in-house real-time PCR (IHRT-PCR), in-house nested cryptic plasmid PCR and in-house nested major outer membrane protein PCR, were performed on genital swabs from 1000 consecutive patients attending a genitourinary medicine clinic. The samples were designated true positive if Chlamydia trachomatis DNA was detected by at least two of the four above-mentioned assays while a sample was defined as true negative if C. trachomatis DNA was detected in only one or none of the assays. By this criterion, there were 129 true positive and 871 true negative samples for C. trachomatis DNA in this cohort. Amplicor PCR designated 144 samples positive: 128 (89%) of 144 samples were true positive and 16 (11%) were false positive. IHRT-PCR detected 126 of 129 true positive samples and did not generate any false positive results. The sensitivity of IHRT-PCR was comparable with, and specificity was higher than, Amplicor PCR for the diagnosis of genital chlamydial infection.