Post-colonoscopy colorectal cancers identified by probabilistic and deterministic linkage: results in an Australian prospective cohort

OBJECTIVE: Post-colonoscopy colorectal cancers (PCCRCs) are recognised as a critical quality indicator. Benchmarking of PCCRC rate has been hampered by the strong influence of different definitions and methodologies. We adopted a rigorous methodology with high-detail individual data to determine PCCRC rates in a prospective cohort representing a single jurisdiction. SETTING: We performed a cohort study of individuals who underwent colonoscopy between 2001 and 2008 at a single centre serving Australian Capital Territory (ACT) and enclaving New South Wales (NSW) region. These individuals were linked to subsequent colorectal cancer (CRC) diagnosis, within 5 years of a negative colonoscopy, through regional cancer registries and hospital records using probabilistic and deterministic record linkage. All cases were verified by pathology review. Predictors of PCCRCs were extracted. PARTICIPANTS: 7818 individuals had a colonoscopy in the cohort. Linkage to cancer registries detected 384 and 98 CRCs for notification dates of 2001–2013 (ACT) and 2001–2010 (NSW). A further 55 CRCs were identified from a search of electronic medical records using International Classification of Diseases-10 diagnosis codes. After verification and exclusions, 385/537 CRCs (58% male) were included. PRIMARY OUTCOME MEASURE: PCCRC rates. RESULTS: There were 15 PCCRCs in our cohort. The PCCRC incidence rate was 0.384/1000 person-years and the 5-year PCCRC risk was estimated as 0.192% (95% CI 0.095 to 0.289). The index colonoscopy prior to PCCRC was more likely to show diverticulosis (p=0.017 for association, OR 3.56, p=0.014) and have poor bowel preparation (p=0.017 for association, OR 4.19, p=0.009). CONCLUSION: In this population-based cohort study, the PCCRC incidence rate was 0.384/1000 person-years and the 5-year PCCRC risk was 0.192%. These data show the ‘real world’ accuracy of colonoscopy for CRC exclusion.