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Updated: Apr 20, 2026
Forward Genetic Approaches in Chlamydia trachomatis
Published on: October 23, 2013
The verification of nucleic acid amplification testing (Gen-Probe Aptima Assay) for chlamydia trachomatis from ocular
Regis P Kowalski1, Lisa M Karenchak1, Leela V Raju1
1The Charles T. Campbell Eye Microbiology Laboratory, Department of Ophthalmology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
Objective:
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.
Design:
Retrospective laboratory verification study.
Subjects:
Patients with infectious conjunctivitis.
Methods:
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.
Main Outcome Measures:
Detection of C. trachomatis rRNA.
Results:
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.
Conclusions:
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.
