The Verification of Nucleic Acid Amplification Testing (Gen-Probe Aptima Assay) for Chlamydia trachomatis from Ocular Samples

Abstract

Chlamydia trachomatis conjunctivitis may present with extended symptoms, and it can have social ramifications as a sexually transmitted disease. For appropriate therapy, C.trachomatis conjunctivitis should be diagnosed definitively. This study presents the verification of nucleic acid amplification testing (NAAT; Gen-Probe Aptima Combo 2 assay) for detection of C.trachomatis ribosomal RNA (rRNA) from direct ocular samples. Retrospective laboratory verification study. Patients with infectious conjunctivitis. A battery of 25 true-positive specimens (direct ocular specimens from patients with symptoms consistent with C.trachomatis conjunctivitis and with previously demonstrated positive polymerase chain reaction [PCR] results for C.trachomatis DNA by Roche Amplicor) and 25 true-negative specimens (direct ocular specimens with culture-positive results for herpes simplex virus [n= 5], adenovirus [n= 5], Haemophilus influenzae [n= 5], and Streptococcus pneumoniae [n= 5]), and transport medium (n= 5) were tested for C.trachomatis rRNA by NAAT. These true-negative specimens have differential etiologic agents of infectious conjunctivitis. The 25 C.trachomatis specimens with PCR-positive results (obtained May 1994-May 2012) and 20 true-negative infectious ocular specimens (obtained December 2008-August 2013) were collected with soft-tipped applicators and placed in transport medium. All excess specimens were stored at-80°C. All samples were centrifuged at 13,000 rpm for 1 hour at 6°C. For each sample, using the Aptima Unisex collection blue swab, a specimen was collected from the conical apex of the storage tube where a pellet was formed. The Aptima Unisex collection swab was placed in a tube of Aptima swab transport medium for testing. All samples were tested in duplicate. Detection of C.trachomatis rRNA. Of 25 true-positive samples, 24 (96%) were positive by NAAT, whereas 25 of 25 true-negative samples (100%) showed negative results. The sensitivity, specificity, positive predictive value, negative predictive value, and efficiency were determined to be 96%, 100%, 100%, 96%, and 98%, respectively. The detection of C.trachomatis in ocular specimens by NAAT was verified for laboratory diagnosis. The test will be evaluated prospectively to determine future test performance precisely.