Harms of colonoscopy in a colorectal cancer screening programme with faecal occult blood test: A population-based cohort study

Abstract Background and aims To assess the harms of colonoscopy in a real world colorectal cancer screening programme with faecal occult blood test. Methods Retrospective cohort study of all colonoscopies performed in patients aged 50–74 for a positive guaiac-based faecal occult blood test between September 2003 and February 2010 within the screening programme in progress in Alsace (France). Adverse events were recorded through prospective voluntary reporting by gastroenterologists and retrospective postal surveys addressed to persons screened and their general practitioners. Results Of 10,277 colonoscopies, 250 adverse events were recorded, 48 (4.7‰, 95% CI 3.4–6.0) of them being moderate or severe, mainly 10 (1.0‰, 95% CI 0.4–1.6) perforations and 31 (3.0‰, 95% CI 2.0–4.1) bleeding. 91.7% of moderate and severe adverse events were the result of a therapeutic procedure. Of 103 serious adverse events, eight (7.8%) were considered preventable. Gastroenterologists reported 52.2% of moderate and severe adverse events. A mild adverse event or an incident was reported in up to 97.0‰ (95% CI 83.2–110.7) colonoscopies. Conclusion The harms of colonoscopy were underestimated in all randomized controlled trials on colorectal cancer screening with faecal occult blood test. They are greater in a real world programme, estimated at 7.5 major and 100 minor adverse events per 1000 colonoscopies.