Objectives To 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 gonorrhoeae across multiple molecular diagnostic platforms.
Methods Cultured N. gonorrhoeae was 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.
Results In total, 2756 samples were processed, with N. gonorrhoeae detected 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).
Conclusions Increased 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. gonorrhoeae was successfully detected, supporting flexibility in sample storage, and by extension the feasibility of analysing self-collected samples to improve access to STI testing.
- NEISSERIA GONORRHOEAE
- PUBLIC HEALTH
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Contributors JAF, MK, DW and SP designed the study. JAF and MK performed technical and statistical analysis. FA assisted with data generation. JAF prepared the figures and JAF, JP, DW and SP prepared the manuscript which was reviewed by all authors. All authors had full access to all the data in the study and had final responsibility for the decision to submit the manuscript. SP is the guarantor for the manuscript.
Funding DW is supported by an NHMRC Investigator Grant (APP1174555). JP and FA are both supported by an Australian Government Research Training Program Scholarship. This work was also supported by an Australian Research Council (ARC) Industrial Transformation Research Hub Grant (IH190100021).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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