The polyp detection rate of colonoscopy: a national study of Medicare beneficiaries.

National-level data on the proportion of colonoscopies in routine practice that result in polyp detection are limited. Our goal was to determine the diagnostic yield of colonoscopy among population subgroups. We reviewed Medicare claims data for all fee-for-service beneficiaries 65 years or older who underwent colonoscopy in 1999. With the use of diagnosis and procedure codes, the proportion of procedures with polyps was estimated. Three different criteria for polyp detection were used. Approximately 1.8 million colonoscopy procedures were identified. Depending on the specific criteria used, 23.9% to 35.7% of examinations noted polyps. The detection rate was highest in younger patients, men, and whites. The apparent yield of colonoscopy in terms of polyp detection is at least 24%. These data may be informative in predicting resource allocation for therapeutic procedures associated with colonoscopy. Future studies should determine the use and yield of serial colonoscopies for polyp surveillance.