The Effect of Race and Sex on Physicians' Recommendations for Cardiac Catheterization

The diagnosis of coronary-artery disease has become increasingly complex. Many different results, obtained from tests with substantial imperfections, must be integrated into a diagnostic conclusion about the probability of disease in a given patient. To approach this problem in a practical manner, we reviewed the literature to estimate the pretest likelihood of disease (defined by age, sex and symptoms) and the sensitivity and specificity of four diagnostic tests: stress electrocardiography, cardiokymography, thallium scintigraphy and cardiac fluoroscopy. With this information, test results can be analyzed by use of Bayes' theorem of conditional probability. This approach has several advantages. It pools the diagnostic experience of many physicians ans integrates fundamental pretest clinical descriptors with many varying test results to summarize reproducibly and meaningfully the probability of angiographic coronary-artery disease. This approach also aids, but does not replace, the physician's judgment and may assit in decisions on cost effectiveness of tests.

There are wide disparities between blacks and whites in the use of many Medicare services. We studied the effects of race and income on mortality and use of services. We linked 1990 census data on median income according to ZIP Code with 1993 Medicare administrative data for 26.3 million beneficiaries 65 years of age or older (24.2 million whites and 2.1 million blacks). We calculated age-adjusted mortality rates and age- and sex-adjusted rates of various diagnoses and procedures according to race and income and computed black:white ratios. The 1993 Medicare Current Beneficiary Survey was used to validate the results and determine rates of immunization against influenza. For mortality, the black:white ratios were 1.19 for men and 1.16 for women (P<0.001 for both). For hospital discharges, the ratio was 1.14 (P<0.001), and for visits to physicians for ambulatory care it was 0.89 (P<0.001). For every 100 women, there were 26.0 mammograms among whites and 17.1 mammograms among blacks. As compared with mammography rates in the respective most affluent group, rates in the least affluent group were 33 percent lower among whites and 22 percent lower among blacks. The black:white rate ratio was 2.45 for bilateral orchiectomy and 3.64 for amputations of all or part of the lower limb (P<0.001 for both). For every 1000 beneficiaries, there were 515 influenza immunizations among whites and 313 among blacks. As compared with immunization rates in the respective most affluent group, rates in the least affluent group were 26 percent lower among whites and 39 percent lower among blacks. Adjusting the mortality and utilization rates for differences in income generally reduced the racial differences, but the effect was relatively small. Race and income have substantial effects on mortality and use of services among Medicare beneficiaries. Providing health insurance is not enough to ensure that the program is used effectively and equitably by all beneficiaries.

Studies have reported that blacks undergo fewer coronary-revascularization procedures than whites, but it is not clear whether the clinical characteristics of the patients account for these differences or whether they indicate underuse of the procedures in blacks or overuse in whites. In a study at Duke University of 12,402 patients (10.3 percent of whom were black) with coronary disease, we calculated unadjusted and adjusted rates of angioplasty and bypass surgery in blacks and whites after cardiac catheterization. We also examined patterns of treatment after stratifying the patients according to the severity of disease, angina status, and estimated survival benefit due to revascularization. Finally, we compared five-year survival rates in blacks and whites. After adjustment for the severity of disease and other characteristics, blacks were 13 percent less likely than whites to undergo angioplasty and 32 percent less likely to undergo bypass surgery. The adjusted black:white odds ratios for receiving these procedures were 0.87 (95 percent confidence interval, 0.73 to 1.03) and 0.68 (95 percent confidence interval, 0.56 to 0.82), respectively. The racial differences in rates of bypass surgery persisted among those with severe anginal symptoms (31 percent of blacks underwent surgery, vs. 45 percent of whites, P<0.001) and among those predicted to have the greatest survival benefit from revascularization (42 percent vs. 61 percent, P<0.001). Finally, unadjusted and adjusted rates of survival for five years were significantly lower in blacks than in whites. Blacks with coronary disease were significantly less likely than whites to undergo coronary revascularization, particularly bypass surgery - a difference that could not be explained by the clinical features of their disease. The differences in treatment were most pronounced among those predicted to benefit the most from revascularization. Since these differences also correlated with a lower survival rate in blacks, we conclude that coronary revascularization appears to be underused in blacks.