Value of repeat testing using Cepheid GeneXpert CT/NG for indeterminate PCR results when diagnosing Chlamydia trachomatis and Neisseria gonorrhoeae. (January 2015)

• Record Type: Journal Article
• Authors: Parcell, Benjamin J; Ratnayake, Lasantha; Kaminski, Geraldine; Olver, William J; Yirrell, David L
• Is Part Of: International journal of STD & AIDS. Volume 26:Number 1(2015:Jan.)
• Page Start: 65
• Page End: 67
• Publication Date: 2015-01
• Subjects: Sexually transmitted infection -- Chlamydia trachomatis -- Neisseria gonorrhoeae -- nucleic acid amplification test -- diagnosis -- indeterminate results -- confirmation -- Cepheid GeneXpert CT/NG; Sexually transmitted diseases -- Periodicals; AIDS (Disease) -- Periodicals; 616.951
• DOI: 10.1177/0956462414531938
• Languages: English
• ISSNs: 0956-4624

Abstract

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 24 h. 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.