One number decides how good a colonoscopy is
Colorectal cancer is one of the leading causes of cancer death worldwide, and it is largely preventable: find the polyp, remove it, and the cancer never forms. The score every endoscopist is judged by is the adenoma detection rate, or ADR: the share of screening colonoscopies in which at least one precancerous adenoma is found.
In a landmark 2014 study in the New England Journal of Medicine, each 1-point rise in a doctor's ADR cut their patients' risk of an interval cancer, one that appears between screenings, by about 3%.[1] The professional benchmark is 25%. Elite endoscopists reach 35 to 50% by washing the lining, flattening folds, and withdrawing the scope slowly for six to nine minutes.
Yet in tandem studies, where a second colonoscopy immediately follows the first, 25 to 35% of adenomas turn out to have been missed, usually because they were flat, tiny, hidden behind a fold, or seen late on a long day.[4]