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Screening could potentially have a beneficial effect on outcome as only half the patients presenting with large bowel cancer have the potential for cure; earlier detection and treatment secures an improved prognosis.

Flexible sigmoidoscopy and colonoscopy are too labour-intensive, but faecal occult blood testing is a more promising technique. The 'Haemoccult' method, for example, uses guaiac resin that has been stabilised on filter paper to detect as little as 2-5 ml of blood passed per 24 hours. However, false positives can result if meat has been eaten in the last three days, and compliance with testing is often poor.

Research is targeting more sensitive and specific means of indicating occult bleeding, e.g. enzyme immunoassays, and of increasing compliance, e.g. a pad that is used to wipe the anus and is then developed. However, the debate on whether screening is cost-effective continues. Using methods that detect occult blood loss assume that all tumours bleed but this is not the case.

Last reviewed 01/2018