Analytic performance and contamination control methods of a ligase chain reaction DNA amplification assay for detection of Chlamydia trachomatis in urogenital specimens

Abstract A ligase chain reaction (LCR) DNA amplification assay that targeted the cryptic plasmid of Chlamydia trachomatis was developed to detect C. trachomatis urogenital tract infection. The objectives of this study were to determine the cutoff and analytic performance of the LCR assay and to characterize the effectiveness of its postdetection contamination control method. The assay's cutoff was determined after receiver-operator characteristic (ROC) analysis of 4660 clinical data points. The assay detected one infectious unit per reaction of each of the 15 C. trachomatis serovars and did not cross-react with 13 Chlamydia pneumoniae strains, 13 Chlamydia psittaci strains, and 87 other bacteria, fungi, parasites, or viruses. In addition, the assay did not detect 77 processed urine specimens collected from patients with urinary tract infections caused by yeast or bacteria other than C. trachomatis . The assay was sufficiently precise to detect consistently two infectious units of C. trachomatis per reaction. False-positive assay results attributable to contamination with amplified product were minimized by the use of standard procedures as well as by a postdetection chemical inactivation method that could reduce the amount of amplified LCR product by a factor of ⩾10 7 .