Background/introduction Varied advice is given to women about testing for chlamydia (CT) and gonorrhoea (NG) whilst menstruating. Some are advised it makes no difference, others are advised not to test or are offered urine sampling instead of a vulvovaginal swab. There is no published evidence to inform such advice.

Aim(s)/objectives To determine if menses affects the performance of CT/NG NAATs.

Methods Using data collected in a large CT/NG NAATs diagnostic study we compared the prevalence of infections in menstruating women versus those not menstruating.

Results Of the 3973 study participants 162 (4%) were menstruating and 3811 were not. 30 (18.5%) menstruating women had CT and 10 (6.2%) had NG; 380 (10%) non-menstruating women had CT and 90 (2.4%) had NG. Menstruating women were more likely to be diagnosed with CT (OR 2.05; p = 0.0008) and NG (OR 2.72; p = 0.0055); less likely to have had a previous STI (OR 0.66) and to have cervicitis (OR 0.21) but more likely to be a STI contact (OR 2.13) and have bacterial STI symptoms (OR 1.36). After adjusting for these confounding variables menstruating women remained more likely to be diagnosed with CT (Adjusted OR 1.98; 95% CI 1.27–3.09; p = 0.003).

Discussion/conclusion Menses does not have a negative effect of the performance of CT/NG NAATs; in fact the prevalence of infections was higher in menstruating women. Only 4% of women were menstruating suggesting that women avoid attending for STI testing during their period unless really necessary. Hence testing should be performed during menstruation using vulvovaginal or endocervical swabs.