Background Patient self-sampling allows for remote collection and return to clinic or laboratory by post. Urine samples, although convenient, are challenging to post. This study evaluated UriSwab (Copan, Brescia, Italy) as a collection and transport vessel for Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG) and Mycoplasma genitalium (MG) detection by polymerase chain reaction, compared with flocked swab and neat urine.
Methods: Five replicates of each specimen type were prepared from previously characterised urine samples (n=330), stored at room temperature (RT) or 37°C, then extracted on day 1, 3, 7, 10 and 16 (VERSANT kPCR Sample Prep System, Siemens, Munich, Germany). Crossing thresholds (Cq) from CT and NG detection (VERSANT CT/GC DNA 1.0 assay kit, Siemens) and MG detection (real-time polymerase chain reaction assay) were compared using logistic regression, stratified by sample type, temperature and analyte. Mixed-model statistical techniques were used to assess correlation between repeated observations.
Results: UriSwab showed an increasing trend in Cq values at RT and 37°C for CT and NG, and RT for MG (all P<0.01). UriSwab was not statistically significantly different to neat urine, except CT at RT (0.83, 95% confidence interval: 0.51-1.15). Flocked swab similarly showed increasing Cq values at 37°C for CT, a significant decreasing trend at RT for MG and increasing trend at 37°C for MG. Flocked swab was not statistically significantly different from neat urine at RT and 37°C for CT and MG.
Conclusion: UriSwab allows transport of urine for CT, NG and MG detection regardless of storage time or temperature, suggesting that CT and NG are stable for up to 16 days and MG up to 10 days.