Background Extra-genital tests for gonorrhoea and chlamydia are important in MSM and are increasingly important in women as vulvovaginal swabs (VVS) alone can miss infections. Self-sampling is frequently used but there has been no robust RCT against clinician-taken samples in MSM or women to assess its efficacy.
Aim To compare self-taken extra-genital samples in women and MSM with clinician-taken samples for diagnostic accuracy.
Methods Women and MSM attending a sexual health clinic were invited into a ‘swab yourself’ trial. Clinician and self-samples were taken from the pharynx and rectum (plus VVS in women and FCU in MSM) for gonorrhoea (NG) and chlamydia (CT) using NAATs. The sampling order was randomised. Patient infected status was defined as at least two positive confirmed samples.
Results 1251 women and MSM were recruited to January 2016. Overall prevalence: NG 5.7% (rectal 4.3%, pharyngeal 3.1%), CT 17.8% (rectal 16.5%, pharyngeal 4.0%). 9.4% of female NG cases and 13.8% of CT cases were VVS negative. 72% of MSM NG cases and 89.5% of CT cases were FCU negative.
Sensitivity, specificity, PPV and NPV are shown in the table:
Conclusion This on-going work is the first randomised study showing that self-taken extra-genital samples have high sensitivity and specificity and are comparable to clinician-taken samples. High levels of extra-genital infections were found. In women 9% of NG and 14% of CT infections would be missed using VVS alone demonstrating the benefit of extragenital sampling.