Case-mix-adjusted mean number of polyps per 100 procedures: a new candidate gold standard colonoscopy key performance indicator

Objective Adenoma detection rate (ADR) has been criticised as a colonoscopy key performance indicator (KPI), for excluding serrated polyps, requiring histological data and fostering a ‘one-and-done’ attitude. We hypothesised that a case-mix-adjusted mean number of polyps (aMNP) would address these criticisms and provide a better measure of colonoscopy quality. We aimed to develop an aMNP using the National Endoscopy Database (NED) and assess its relationship with quality metrics. Methods We extracted colonoscopy data from NED for 1 January 2019–4 April 2019. Multiple negative binomial regression was undertaken to estimate effects of patient variables on MNP and generate aMNP. Associations between aMNP and polyp detection rate (PDR), proximal polypectomy rate (PPR), postcolonoscopy colorectal cancer (PCCRC) rate and Joint Advisory Group for GI endoscopy (JAG) Global Rating Scale (GRS) were explored. Results 92 892 colonoscopies were analysed. Patient age, sex and procedure indication were significantly associated with MNP and used to create aMNP. At endoscopist level, aMNP strongly correlated with PDR (Spearman rho=0.834, p<0.001) and PPR (rho=0.709, p<0.001). Median aMNP was significantly lower in Trusts with higher versus lower PCCRC rates (73.9 vs 67.0 polyps per 100 procedures, p=0.047) and higher in units with GRS A/B versus C/D (aMNP 63.5 vs 55.2, p<0.001). Conclusions We demonstrate a method to compute a novel case-mix-adjusted KPI, aMNP, which is significantly associated with PDR, PPR, PCCRC and JAG GRS. Histological data were unavailable. aMNP addresses many limitations of ADR, adjusts for warranted variation in detection, and hence may improve audit and feedback engagement. We propose it as a candidate gold standard KPI for reporting endoscopy quality.