Regis P Kowalski1, Lisa M Karenchak2, Leela V Raju2, Nahed Ismail3. 1. The Charles T. Campbell Eye Microbiology Laboratory, Department of Ophthalmology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania. Electronic address: kowalskirp@upmc.edu. 2. The Charles T. Campbell Eye Microbiology Laboratory, Department of Ophthalmology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania. 3. Division of Clinical Microbiology, Department of Pathology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
Abstract
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.
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.