Introduction Adenoma detection rate (ADR) is a key performance indicator for colonoscopy. Evidence suggests that various factors influence ADR. The BSG quality and safety indicators for endoscopy and the Global Rating Scale recommend ADR>10%.

Methods To assess how case mix affects ADR in a tertiary centre. We analysed 25 consecutive colonoscopies from each of the 15 non-trainee endoscopists at our institution. A further 50 cases each from six of the 15 endoscopists with low ADR, were assessed. Indications were divided into high (polyp follow-up, surveillance, familial cancer syndromes, rectal bleeding, anaemia) and low risk (IBD, diarrhoea, constipation, pain).

Results Six endoscopists had a median ADR of 8% (0–16%). The other nine had a median ADR of 28% (24–40%) with significantly more high-risk indications (p<0.0001). A further 50 cases from each of the six endoscopists with lower ADR were analysed. Median ADR was 12% (8–22%).

Conclusion In the 50 cases analysed for each of the six colonoscopists with low ADR, there were significantly more low risk cases (p<0.0001). The ADR was significantly lower for the low risk cases (2.6% vs 22.6%, p<0.0001). ADR should be measured as a key performance indicator in the context of indication for colonoscopy.