Population based randomised study of uptake and yield of screening by flexible sigmoidoscopy compared with screening by faecal occult blood testing

Objectives: To compare the feasibility of mass screening by flexible sigmoidoscopy with screening by faecal occult blood testing (Haemoccult) and both tests combined. Design: Patients were randomised to screening by flexible sigmoidoscopy, faecal blood testing, or both tests. The flexible sigmoidoscopy examinations were performed by a general practitioner. Setting: General practice. Subjects: 3744 patients aged 50-75 years. Main outcome measures: Uptake, positive results, detection of neoplasia, complications, and recall for diagnostic colonoscopy. Results: Uptake was significantly higher in the flexible sigmoidoscopy group (46.6%) than in the faecal blood test group (31.6%; P<0.001) or than in the group having both tests (30.1%; P<0.001). Telephone reminders increased uptake of sigmoidoscopy to 61.8%. In total, 1116 sigmoidoscopy examinations were performed without major complication. Polyps were found in 19.3% (95% confidence interval 17.0% to 21.6%) but only 6.8% (5.3% to 8.3%) had adenomas and 2.4% (1.5% to 3.3%) “high risk” adenomas. Cancer was detected in four subjects. The faecal blood test yielded positive results in 0.8% (0.2% to 1.4%) but missed at least one cancer and 30 cases of adenoma which were found by sigmoidoscopy in the combined group. Use of histological criteria—shown elsewhere to correlate with future risk of colorectal cancer—to select “positive” patients could reduce recall for diagnostic colonoscopy from about 20% to less than 5%. Conclusions: Some of the predicted obstacles to screening with flexible sigmoidoscopy are surmountable. Clear evidence relating to efficacy will be obtained only from a randomised controlled trial.