Open AccessDespite Excellent Test Characteristics of the cobas 4800 CT/NG Assay, Detection of Oropharyngeal Chlamydia trachomatis and Neisseria gonorrhoeae Remains Challenging
Author(s) -
Julius M. van Niekerk,
Brian M. J. W. van der Veer,
Christian J. P. A. Hoebe,
J. van de Bovenkamp,
Cmc van Herk,
Inge H. M. van Loo,
Lieke B. van Alphen,
Petra Wolffs
Publication year - 2021
Publication title -
journal of clinical microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.349
H-Index - 255
eISSN - 1070-633X
pISSN - 0095-1137
DOI - 10.1128/jcm.02137-20
Subject(s) - chlamydia trachomatis , neisseria gonorrhoeae , nucleic acid amplification tests , chlamydiales , chlamydia , chlamydiaceae , virology , medicine , neisseriaceae , neisseria , biology , microbiology and biotechnology , immunology , bacteria , antibiotics , genetics
Oropharyngeal Chlamydia trachomatis (CT) infections and, especially, Neisseria gonorrhoeae (NG) infections are common, but few commercial nucleic acid amplification tests (NAATs) specify extragenital samples for intended use. The test characteristics of the cobas 4800 CT/NG assay were evaluated for oropharyngeal swabs. The technical validation included analysis of the specificity, sensitivity, dynamic range, linearity, efficiency, and precision. The probability of detection curve combined with historical data enabled the estimation of potentially missed diagnoses. A clinical evaluation was performed on a subset of 2,798 clinical samples available from routine diagnostics. Results of the cobas 4800 were compared with those from in-house C. trachomatis / N. gonorrhoeae PCR assays. Discrepant samples were tested with resolver assays, and these results were considered decisive. No cross-reactivity was seen in the analytical specificity analysis. High linearity ( R 2 ≥ 0.983), efficiency (89% to 99%), and precision (cycle threshold [ C T ] value of 0.1 to 0.9) were seen for both C. trachomatis and N. gonorrhoeae The limit of detection in oropharyngeal samples was 3.2 × 10 2 inclusion-forming units (IFU)/ml for C. trachomatis and 6.7 × 10 2 CFU/ml for N. gonorrhoeae Estimates on potentially missed diagnoses were up to 7.2% for C. trachomatis and up to 24.7% for N. gonorrhoeae Clinical sensitivity and specificity were evaluated with 25 C. trachomatis -positive, 86 N. gonorrhoeae -positive, and 264 negative samples, resulting in 100% and 99.6% for C. trachomatis and 100% and 96.7% for N. gonorrhoeae, respectively. The findings in this study demonstrate the utility of the cobas 4800 CT/NG assay for oropharyngeal samples. Despite its being a highly accurate test, the range of reported C T values, especially for N. gonorrhoeae , suggests relatively low oropharyngeal loads. Hence, consistent detection over the full range of oropharyngeal loads could be impaired.