The potential use of midstream urine samples for diagnosing Chlamydia/Gonorrhoea NAAT in male and female patients, and the pre-analytical storage conditions in neat urine specimens.

Current recommendations for screening Chlamydia trachomatis (CT) and Neisseria gonorrhoeae in urinary tract infections using nucleic acid amplification tests (NAATs) include vaginal swabs for women and first‑catch urine for men. In addition, some manufacturers require the use of a transport medium for prolonged pre‑analytical storage. The aim of this study was to evaluate the sensitivity and specificity of midstream urine specimens and to assess nucleic acid stability in neat urine samples stored at +4°C. The study included 338 asymptomatic participants undergoing screening for Chlamydia trachomatis and Neisseria gonorrhoeae as part of the French national STI screening program (172 women and 166 men). For each participant, a reference specimen (self‑collected vaginal swab for women and first‑catch urine for men) was compared with a midstream urine sample. Two comparisons were conducted to assess nucleic acid stability: the first compared urine stored in a preservation medium with neat urine stored at +4°C, and the second compared neat urine stored at +4°C on days 1 and 7. All samples were analysed using the Alinity m Abbott® automated system with the STI AMP Kit. Among the 46 positive samples, the prevalence of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) was 43/338 and 4/338, respectively. Due to the low prevalence of NG, sensitivity and specificity analyses for midstream urine were limited to CT. Vaginal swabs showed superior performance for detecting CT in females, with two infections missed by midstream urine. Midstream urine demonstrated adequate sensitivity in females (92.9%) and excellent sensitivity in males (100%), with no false-positive results observed. Regarding nucleic acid stability, no statistical difference (p=0.799) was observed for cycle values between urine samples eluted into the liquid medium and neat urine stored at +4°C. Furthermore, our study validated the use of prolonged storage periods (up to 7 days) at +4°C for CT and NG detection in neat urine (p=0.671). In conclusion, the results of this study corroborate the CDC's 2014 recommendations, but the use of midstream urine could offer interesting prospects for Chlamydia trachomatis screening in specific populations. Regarding Neisseria gonorrhoeae, given the low prevalence of positive results found in our study, no meaningful conclusions can be drawn.