Evaluating preanalytical sample storage parameters for nucleic acid-based detection ofNeisseria gonorrhoeae

Abstract

ObjectivesTo ensure accurate diagnosis of infectious diseases, preanalytical factors should be considered when assessing specimen quality and subsequent test result. Accordingly, we aimed to systematically assess the effect of storage time, temperature and buffer on the analytical sensitivity of detecting the sexually transmitted pathogen,Neisseria gonorrhoeaeacross multiple molecular diagnostic platforms.MethodsCulturedN. gonorrhoeaewas spiked into generic and commercial storage buffers and stored at four temperatures and five time points, ranging from −20°C to 37°C, over 30 days. Samples were processed using the Alinity m STI, Xpert CT/NG and Aptima Combo 2 nucleic acid amplification assays and an in-house quantitative PCR assay. A reduction in analytical sensitivity was defined as a significant (p<0.05) increase in cycle threshold (Ct) value relative to control samples.ResultsIn total, 2756 samples were processed, withN. gonorrhoeaedetected in 99.2% of samples. With respect to time, analytical sensitivity was maintained from day 2 (113/120; 94.2%) up to day 30 (110/120; 91.7%) relative to baseline samples. With respect to temperature, analytical sensitivity was maintained from −20°C (147/150; 98.0%) up to 37°C (136/150; 90.7%) relative to baseline samples. Generic buffers, Viral Transport Medium and Amies Liquid Media showed a reduction in analytical sensitivity compared with their commercial counterparts, Aptima Multitest Swab Transport Media and Abbott Alinity transport buffer using select diagnostic assays; this reduction appeared temperature dependent, with the largest differences in median Ct values observed at 37°C (p<0.05).ConclusionsIncreased prevalence of sample self-collection for sexually transmitted infections (STIs) warrants an evaluation of preanalytical sample storage variables on diagnostic testing performance. Here, across a range of time points, temperatures and storage buffers,N. gonorrhoeaewas successfully detected, supporting flexibility in sample storage, and by extension the feasibility of analysing self-collected samples to improve access to STI testing.