Swab-yourself trial with economic monitoring and testing for infections collectively (SYSTEMATIC): Part 1. A diagnostic accuracy, and cost-effectiveness, study comparing clinician-taken versus self-taken rectal and pharyngeal samples for the diagnosis of gonorrhoea and chlamydia

Background Urogenital testing misses extragenital Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT). Extragenital self-sampling is frequently undertaken despite no robust randomized, controlled trial evidence of efficacy. We compared clinician-taken rectal and pharyngeal samples with self-taken samples for diagnostic accuracy and cost in men who have sex with men (MSM) and in females.

Methods This was a prospective convenience sample from a UK sexual health clinic. We randomized the order of clinician- and self-taken samples from the pharynx and rectum, plus first catch urine (MSM) and vulvovaginal swabs (females), for NG/CT detection.

Results Of 1793 participants (1284 females, 509 MSM), 116 had NG detected (75 urogenital, 83 rectum, 72 pharynx); 9.4% infected females and 67.3% MSM were urogenital-negative. A total of 276 had CT detected (217 urogenital, 249 rectum, 63 pharynx); 13.1% infected females and 71.8% MSM were urogenital-negative. Sexual history did not identify those with rectal infections. There was no difference in diagnostic accuracy between clinician- and self-taken samples from the rectum or pharynx. Clinicians took swabs more quickly than participants, so costs were lower. However, in asymptomatic people, nonqualified clinicians would oversee self-swabbing making these costs lower.

Conclusions There was no difference in the diagnostic accuracy of clinician-taken compared with self-taken extragenital samples. Sexual history did not identify those with rectal infections, so individuals should have extragenital clinician- or self-taken samples. Clinician-taken swabs cost less than self-taken swabs; however, in asymptomatic people or those who perform home testing, the costs would be lower than for clinician-taken swabs.

Clinical Trials Registration NCT02371109.