Those who require such evidence consider the endorsement of whole-bowel screening to be premature. Those who accept this implicit evidence of benefit question the ethics of waiting for mortality data. If one selects tests on the basis of their accuracy, colonoscopy wins. It enables inspection of the entire colon, detection of almost all important neoplasms, and immediate polypectomy. Barium enema also enables whole-bowel examination but is less accurate.
Flexible sigmoidoscopy is as accurate as colonoscopy, but only for the distal bowel.
Approximately 85 percent to 90 percent of positive screening tests are false positives. Performing fecal occult-blood screening together with sigmoidoscopy improves sensitivity for lesions that elude sigmoidoscopy alone but not for nonbleeding lesions, particularly polyps. Some contend that accuracy matters less than the magnitude of benefit. Some would say that this is immaterial if screening saves lives and that only those concerned about costs would think otherwise. The answer depends, of course, on the seriousness of the harms.