title: Evaluation of Gen-Probe APTIMA-based Neisseria gonorrhoeae and Chlamydia trachomatis confirmatory testing in a metropolitan setting of high disease prevalence.
abstract: Prompted by reports challenging the validity of the low-positive Neisseria gonorrhoeae and Chlamydia trachomatis results generated by the APTIMA Combo 2 assay (Gen-Probe, Incorporated) and by a Centers for Disease Control and Prevention recommendation to confirm N. gonorrhoeae- or C. trachomatis-positive screens by using an alternative amplification target, we report on a comparison of this means of confirmation with an in-house algorithm of repeat testing. Primary clinical specimens yielding N. gonorrhoeae- or C. trachomatis-specific luminescent values between 100,000 and 1,000,000 were repeat tested in duplicate. A subset of specimens was forwarded for confirmatory assays (Gen-Probe) individualized for alternative N. gonorrhoeae or C. trachomatis targets. An 18-month audit revealed that 230 of 29,977 C. trachomatis screens (0.8%) and 41 of 29,064 N. gonorrhoeae assays (0.1%) yielded low-positive data. When a subset of 40 low-positive N. gonorrhoeae screens was repeat tested, 20 (50.0%) remained positive; 22 (55.0%) of the screens remained positive following performance of the confirmatory assay. In contrast, repeat testing of 153 low-positive C. trachomatis screens yielded a positive result for fewer specimens (n = 97; 63.4%) than when commercial confirmatory testing was used (n = 124; 81.0%). However, confirmation of the results for additional C. trachomatis screens by use of an alternative target did not translate into significant differences in the calculated overall C. trachomatis-positive screen rates (7.39% by repeat testing versus 7.52% by the confirmatory assay; P = 0.53). Furthermore, use of the confirmatory assay raised the positive predictive value only 1.8% over that of repeat testing. Molecular confirmatory testing did not significantly enhance the reliability of C. trachomatis- or N. gonorrhoeae-specific nucleic acid amplification testing in this metropolitan setting compared to the reliability of repeat testing.
authors.affiliation: Wheaton Franciscan and Midwest Clinical Laboratories, Wauwatosa, Wisconsin 53226, USA. Erik.Munson@wfhc.org
authors.forename: Erik
authors.initials: E
authors.lastname: Munson
authors.forename: Vivian
authors.initials: V
authors.lastname: Boyd
authors.forename: Jolanta
authors.initials: J
authors.lastname: Czarnecka
authors.forename: Judy
authors.initials: J
authors.lastname: Griep
authors.forename: Brian
authors.initials: B
authors.lastname: Lund
authors.forename: Nancy
authors.initials: N
authors.lastname: Schaal
authors.forename: Jeanne E
authors.initials: JE
authors.lastname: Hryciuk
mesh_terms: D001431:Bacteriological Techniques / Q000379:methods*; D002690:Chlamydia Infections / Q000382:microbiology*; D002692:Chlamydia trachomatis / Q000235:genetics / Q000302:isolation & purification*; D006069:Gonorrhea / Q000382:microbiology*; D006801:Humans; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D009344:Neisseria gonorrhoeae / Q000235:genetics / Q000302:isolation & purification*; D011237:Predictive Value of Tests; D011933:Reagent Kits, Diagnostic
chemical_list: D011933:Reagent Kits, Diagnostic