Value of repeat testing using Cepheid GeneXpert CT/NG for indeterminate PCR results when diagnosing Chlamydia trachomatis and Neisseria gonorrhoeae

Benjamin J. Parcell (Lead / Corresponding author), Lasantha Ratnayake, Geraldine Kaminski, William J. Olver, David L. Yirrell

    Research output: Contribution to journalArticlepeer-review

    3 Citations (Scopus)


    Nucleic acid amplification tests (NAATs) are the most sensitive method for diagnosing chlamydia and gonorrhoea. We use the COBAS 4800 CT/NG combined assay (Roche Molecular Diagnostics, CA, USA), and whilst the majority of samples yield definitive results, a small proportion are reported as indeterminate. In these instances, it is usual practice to request repeat samples which delays diagnosis. This audit was twofold: first to establish the proportion of indeterminate results with current NAAT testing requiring re-sampling. Second, to determine whether a second NAAT such as Cepheid GeneXpert CT/NG assay (Cepheid, CA, USA) could be used on initial indeterminate samples to resolve indeterminate results, therefore reducing need for repeat sampling. During 2012, 144/21,931 (0.66%) samples were indeterminate for Neisseria gonorrhoeae, Chlamydia trachomatis or both, and a repeat sample was received in only 51.77% of patients with final results being delayed for more than 24h. Over the next six months, there were 77/9472 (0.81%) indeterminate results. After an evaluation and introduction of the Cepheid assay, the number of indeterminate results fell to 9 (0.10%). Thus, use of the Cepheid assay significantly reduced indeterminate results, reduced reliance on a repeat sampling and significantly improved turnaround time, laboratory workflow and patient experience.

    Original languageEnglish
    Pages (from-to)65-67
    Number of pages3
    JournalInternational journal of STD & AIDS
    Issue number1
    Early online date8 May 2014
    Publication statusPublished - Jan 2015

    Fingerprint Dive into the research topics of 'Value of repeat testing using Cepheid GeneXpert CT/NG for indeterminate PCR results when diagnosing <em>Chlamydia trachomatis</em> and <em>Neisseria gonorrhoeae</em>'. Together they form a unique fingerprint.

    Cite this