Differences in Generalists' and Cardiologists' Perceptions of Cardiovascular Risk and the Outcomes of Preventive Therapy in Cardiovascular Disease

Recent changes in the medical marketplace that limit access to specialty care have spurred much debate about the quality of care provided by generalists and specialists [1]. Previous research has compared generalists' and specialists' knowledge and practices with regard to diseases such as rheumatoid arthritis and myocardial infarction, for which it can be reasonably argued that specialists have greater expertise [2-4]. However, the relative expertise of generalists and specialists in primary prevention, which is particularly central to primary care practice, is unknown. Previous research has suggested that some patients may not accept primary preventive therapy if presented with information about the true risk for disease at baseline and about the actual benefits of therapy [5]. Furthermore, the value of a preventive intervention to an individual person may differ from expert consensus that is based on population studies [6-9]. Given these findings, physicians should transmit accurate knowledge to patients about the extent to which they are at risk for cardiovascular disease, so that patients can make informed decisions. In our study, we surveyed practicing family physicians, general internists, and cardiologists to assess their quantitative perceptions of baseline cardiovascular risk and of the benefit of drug therapy for two groups of patients who frequently receive primary preventive therapy: middle-aged men with hypercholesterolemia and elderly persons with isolated systolic hypertension. We also examined a tertiary prevention intervention [10]: coronary artery bypass graft surgery in patients with stable angina and left main coronary stenosis. Because generalists are responsible for most primary prevention, we expected that their estimates of risk at baseline and after therapy would be more accurate than cardiologists' estimates for the primary preventive interventions, but less accurate for the tertiary care intervention. Methods Questionnaire The questionnaire consisted of written case simulations of patients with hypercholesterolemia, isolated systolic hypertension, and chronic stable angina with left main coronary stenosis whose clinical characteristics were representative of the average person in well-publicized clinical trials (Table 6). The hypercholesterolemia case simulation (or scenario) was extrapolated from the Lipid Research Clinics and Helsinki trials [11, 12]; physicians were asked to give unprompted estimates of 5-year risk for myocardial infarction with and without lipid-lowering drug therapy. In the section of the questionnaire dealing with the isolated systolic hypertension scenario, which was derived from the Systolic Hypertension in the Elderly Program trial [13], physicians were asked to give estimates of 5-year risk for stroke with and without antihypertensive drug therapy. In the section that provided the left main coronary stenosis scenario, which was extrapolated from the Veterans Administration Cooperative Study of Surgery for Coronary Arterial Occlusive Disease and the Collaborative Study in Coronary Artery Surgery [14, 15], physicians were asked to estimate 3-year survival with and without coronary artery bypass graft surgery. The correct answers were taken from the results of the studies from which each scenario was derived. Respondents were asked not to consult the literature when completing the questionnaire, but simply to give their best estimates. Appendix Table* The physicians were also asked whether they would generally recommend therapy for such a patient (yes or no). They rated their confidence in their estimates and their familiarity with the relevant medical literature on 7-point Likert-type scales (for example, 1 equals not at all confident; 7 equals very confident). Finally, respondents reported their age, sex, practice setting, specialty (cardiology, general internal medicine, or family practice), and the year in which they graduated from medical school. Sample Selection and Survey Procedure Sampling was done in two stages. First, an addressing company contracted by the American Medical Association (AMA) drew a self-weighted, nationally representative, systematic sample of 6000 practicing physicians (2417 family physicians, 2901 general internists, and 682 cardiologists) from the AMA masterfile of all licensed physicians. Second, after dividing the first-stage sample into the three specialty groups, we selected three separate simple random samples of 199 family physicians, 200 general internists, and 200 cardiologists to form our mailed sample (Table 1). For the cholesterol scenario, using a two-sample t-test, a standard deviation of 8 percentage points from a pilot study, and a 50% response rate, 200 physicians in each group would have given us more than 90% power ( equals 0.05) to detect a difference of 4 percentage points between the groups' estimates. We mailed the two-page survey three times between September 1993 and February 1994, and a reminder postcard was sent 2 weeks after the second mailing. Table 1. Demographic Characteristics of Physicians in the Population and the Sample, by Specialty* Analysis Self-reported specialty was compared with the specialty category in the AMA masterfile, with a percent agreement of 91%. Because the AMA specialty category was used for demographic comparison with the nonrespondents and overall population, we used the specialty designation from the AMA masterfile. The sex of all nonrespondents was inferred on the basis of first name when possible, before the names were deleted. Sex could not be determined in 2% of instances. Characteristics of the AMA masterfile population were estimated from 1993 year-end data [16]. Absolute risk reduction was calculated as the difference between estimated risk at baseline and after therapy. Relative risk reduction was the absolute risk difference divided by the baseline risk. Accuracy was defined as the absolute value of the difference between the physician's estimate and the estimate from the literature, with lower numbers indicating greater accuracy. Because the estimates and accuracy were not normally distributed, we present median estimates with interquartile ranges (the range between the 25th and 75th percentiles). Across specialty groups, we generated differences in medians with confidence intervals, and used the Mann-Whitney U test [17]. Similarly, within each specialty group, we compared the differences in medians between those who would and those who would not recommend treatment. To compare respondents' and nonrespondents' sex and geographic region, we used the Cochran-Mantel-Haenszel chi-square statistic for contingency tables stratified by specialty [18]. For analyses of categorical variables across specialty groups, we did chi-square tests and calculated confidence intervals. Across specialty groups, we also used analysis of variance to generate differences in means and confidence intervals for comparisons of 1) confidence in estimates and 2) familiarity with the relevant literature [both of which were measured on 7-point Likert-type scales], as well as 3) years since graduation from medical school. The relation between these three variables and accuracy was assessed using the Spearman rank correlation coefficient, with confidence intervals generated using the Fisher Z transformation. For clarity, 95% CIs are given throughout. Because of multiple comparisons, we defined statistical significance at the P 0.005 level (two-tailed) and noted trends at the P 0.05 level. Results Respondents and Nonrespondents We received responses from 232 (40%) of 579 eligible physicians. Of the 20 ineligible physicians, 15 did not have a forwarding address and 5 were retired or deceased. Another 5 surveys were illegible, leaving 227 for analysis. Thus, 84 (44%) of 191 eligible family physicians, 77 (40%) of 194 general internists, and 66 (34%) of 194 cardiologists responded (Table 1). The available demographic characteristics of respondents were reasonably similar to those of nonrespondents and of the AMA masterfile population (Table 1). Estimates and Treatment Recommendations For both primary prevention scenarios, cardiologists gave lower, more accurate estimates of baseline risk and absolute risk reduction than either general internists or family physicians, although these estimates were inflated and widely distributed for all three specialties (Table 2). For example, 27% of general internists and more than 30% of family physicians estimated that the 5-year absolute risk reduction for myocardial infarction in the cholesterol scenario was greater than 10%, a 10-fold overestimate, compared with only 14% of cardiologists. Similarly, for the systolic hypertension scenario, half of the family physicians and general internists gave two- to threefold overestimates of the 5-year risks for stroke both with and without antihypertensive therapy, whereas most of the cardiologists better approximated the estimate from the literature. Despite differing perceptions of baseline risk and absolute risk reduction, the specialties did not differ significantly as to estimates of relative risk reduction for the primary prevention scenarios. Table 2. Estimates of Baseline Risk, Absolute Risk Reduction, and Relative Risk Reduction, by Specialty* For the left main coronary stenosis case, cardiologists gave lower estimates of baseline survival and greater estimates of its improvement with surgery (Table 2) than general internists and family physicians, but no differences in accuracy (the absolute value of the difference between the physician's estimate and the estimate from the literature) were seen across the specialties. For example, for the absolute improvement in survival after bypass surgery, no differences in median accuracy were noted between cardiologists and either family physicians (point estimate for the difference in medians, 0; 95% CI, 1 to 5) or general internists (point estimate, 0; CI, 5 to 3). Nonethel