Abstract
BackgroundExtra-genital Neisseria gonorrhoeae and Chlamydia trachomatis infections are mostly asymptomatic, and important reservoir sites of infection as they often go undetected and may be more difficult to eradicate with recommended therapeutic regimens. Commercial nucleic acid amplification tests (NAATs) have not received regulatory approval for the detection of N. gonorrhoeae and C. trachomatis in extra-genital specimens. The HOLOGIC® APTIMA Combo2 assay for N. gonorrhoeae and C. trachomatis has performed well in evaluations using extra-genital specimens.MethodsWe assessed the performance of an in-house real-time duplex PCR assay for the detection of N. gonorrhoeae and C. trachomatis in urine and extra-genital specimens using the HOLOGIC® APTIMA assays as gold standard comparators. Urine, oropharyngeal and ano-rectal specimens were collected from each of 200 men-who-have-sex-with-men (MSM) between December 2011 and July 2012.ResultsFor N. gonorrhoeae detection, the in-house PCR assay showed 98.5–100% correlation agreement with the APTIMA assays, depending on specimen type. Sensitivity for N. gonorrhoeae detection was 82.4% for ano-rectal specimens, 83.3% for oropharyngeal specimens, and 85.7% for urine; and specificity was 100% with all specimen types. The positive predictive value (PPV) for N. gonorrhoeae detection was 100% and the negative predictive value (NPV) varied with sample type, ranging from 98.5–99.5%. For C. trachomatis detection, correlation between the assays was 100% for all specimen types. The sensitivity, specificity, PPV and NPV of the in-house PCR assay was 100% for C. trachomatis detection, irrespective of specimen type.ConclusionThe in-house duplex real-time PCR assay showed acceptable performance characteristics in comparison with the APTIMA® assays for the detection of extra-genital N. gonorrhoeae and C. trachomatis.
Highlights
Extra-genital Neisseria gonorrhoeae and Chlamydia trachomatis infections are mostly asymptomatic, and important reservoir sites of infection as they often go undetected and may be more difficult to eradicate with recommended therapeutic regimens
We evaluated the performance characteristics of the DNA-based in-house duplex Polymerase chain reaction (PCR) assay in comparison to the rRNA-based HOLOGIC® APTIMA assays (APTIMA Combo 2 or APTIMA GC +/− APTIMA CT) for the detection of N. gonorrhoeae and C. trachomatis in urine and extra-genital specimens
Discordant results for N. gonorrhoeae were observed for two specimens (1.0%) that tested negative with the in-house duplex PCR assay, but positive with APTIMA Combo 2 as well as the APTIMA GC assays
Summary
Extra-genital Neisseria gonorrhoeae and Chlamydia trachomatis infections are mostly asymptomatic, and important reservoir sites of infection as they often go undetected and may be more difficult to eradicate with recommended therapeutic regimens. Published data support the fact that commercial nucleic acid amplification tests (NAATs) are more sensitive than culture for the diagnosis of N. gonorrhoeae and C. trachomatis infections across a range of specimen types and under varying conditions [4, 5, 9]. Cell culture was performed for the detection of C. trachomatis in both genital and extra-genital specimens [12, 13] These culture methods are time-consuming, expensive and labour intensive procedures that require specific and careful specimen handling and transport conditions for viable organisms to reach the laboratory [3, 10, 12, 14]. NAAT specificity varies by assay used and by anatomical site screened [7, 12, 15, 18, 19]
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