A novel real-time PCR to detect Chlamydia trachomatis in first-void urine or genital swabs

Abstract

Screening for Chlamydia trachomatis infections can be performed on urine samples and genital swabs using molecular techniques. A novel approach was developed that combined an automated extraction procedure, an automated liquid-handling system and real-time PCR to detect C. trachomatis from urine or swabs. This novel real-time PCR approach was compared to the commercial Cobas Amplicor system on 628 specimens. In a retrospective analysis, 51 samples that tested positive using the Cobas assay were also positive with the real-time PCR, whereas the 49 samples negative with Cobas were also negative with the real-time PCR, for an overall agreement of 100 %. Among 528 prospective samples consecutively received at the authors' laboratory with a request for C. trachomatis PCR, five PCR reactions were inhibited when tested with Cobas. These five inhibited samples were found negative with the real-time PCR. Among the remaining 523 samples, 45 (8.6 %) were positive with both methods, 476 (91 %) were negative with both methods, and 2 (0.4 %) were positive with Cobas but negative with the real-time PCR. Thus, when considering Cobas as the gold standard, the overall agreement was 99.6 %, the sensitivity of the real-time PCR was 95.7 % and the specificity was 100 %. The two discrepant samples were retested in parallel and were found negative with both methods. When testing a batch of 25 samples, both reagent costs and laboratory technician time were reduced with the new technique (7.30 euros per sample and 134 min) compared to Cobas (11.20 euros per sample and 232 min). Moreover, due to reduced organizational constraints, the median time from sample reception to result was only 24 h using the automated platform. Overall, this novel real-time PCR approach exhibited an excellent specificity and a sensitivity similar to that of Cobas Amplicor PCR for the detection of C. trachomatis. Given its high throughput potential and low costs/laboratory technician time requirement, it may be useful for future use in large C. trachomatis screening programs.