Does inappropriate use explain geographic variations in the use of health care services? A study of three procedures.

We studied the appropriateness of use of coronary angiography, carotid endarterectomy, and upper gastrointestinal tract endoscopy and its relationship to geographic variations in the rates of use of these procedures. We selected geographic areas of high, average, and low use of these procedures and randomly sampled Medicare beneficiaries who had received one of the procedures in 1981. We determined the indications for the procedures using a detailed review of medical records and used previously developed ratings of appropriateness to assign an appropriateness score to each case. Differences among sites in levels of appropriateness were small. For example, in the high-use site for coronary angiography, 72% of the procedures were appropriate, compared with 81% in the low-use site. Coronary angiography was performed 2.3 times as frequently in the high-use site compared with the low-use site. Under the conditions of this study, we did find significantly levels of inappropriate use: 17% of cases for coronary angiography, 32% for carotid endarterectomy, and 17% for upper gastrointestinal tract endoscopy. We conclude that differences in appropriateness cannot explain geographic variations in the use of these procedures.