Horner et al. examine several plausible explanations for racial disparities in the use of diagnostic and therapeutic procedures for patients with cerebrovascular disease, with an emphasis on carotid endarterectomy and angiography. The evidence is reviewed based on its “its support, or reputation.”

The authors cite several studies suggesting that pathophysiological differences may, in theory, account for significant racial differences in the extent and location of atherosclerotic disease. Several hypotheses have been postulated which claim that “some populations, including blacks, in which hypertension and diabetes are prevalent, will experience more ischemic strokes that involve the smaller cerebral arteries. Empirical evidence is based on autopsy of patients who died from stroke, case series of patients who have received ultrasonography or arteriography of their carotid arteries, and studies of patients receiving angiography. Analyses “have indicated that stenosis of the middle cerebral arteries (i.e., intracranial arteries) is more prevalent among black patients, whereas extracranial artery stenosis is less prevalent.” This former type of pathology is not amenable to surgery. However, despite evidence suggesting that fewer blacks may be candidates for surgery, no study has determined if racial differences exist among a cohort that has clinical indications for surgical procedures. Horner et al cite no evidence or studies ascertaining racial differences in the diagnostic workup for evaluation of cerebrovascular disease.

The authors also discuss a second theory that the “observed patterns of utilization of expensive diagnostic or therapeutic procedures reflect the ability to pay for care.” The authors state that across studies “with and without adjustment for income, the relative odds of whites versus blacks undergoing carotid endarterectomy are approximately three.” This degree of disparity has been reported “across hospitals with different reimbursement arrangements.” The hospitals studied ranged from private sector hospitals to Veterans Affairs Hospitals. “Thus,” the authors conclude “among hospitalized patients, ‘ability to pay’ does not appear to explain a significant amount of the racial variation in the use of carotid endarterectomy.” Besides, evidence of the socioeconomic impact on care is only available when the patient is referred by the physician and receives outpatient diagnostic care or when the patient has been referred for more invasive diagnostic evaluation and treatment in the inpatient setting. As the authors suggest, the effect of racial bias and/or ability to pay “ may be a particularly important factor earlier in the process of care when the presenting signs and symptoms are vaguer and, hence, the approach to clinical management is less clear.”

The third theory proposed is that patient decisions regarding their care differ by race. There is, however, no documented study indicating that differences in patient preference for care explain racial disparities in the use of carotid endarterectomy or other invasive procedures. The authors extrapolate from studies examining racial differences in cardiac care. Several of these studies suggest that black patients delay seeking care for possible myocardial infarction. Studies of cardiac care have also indicated that acceptance of the physician’s recommendation varies by race. One such study found a higher refusal rate among black patients (Maynard, 1986). However this study also revealed that “surgery was recommended less often to blacks than to whites, despite similar clinical and angiographic characteristics.”

After analyzing the available studies documenting racial difference in the use of carotid endarterectomy, the authors suggest several areas for further research. First, “possible bias in the selection of patients for either noninvasive or invasive diagnostic and therapeutic procedures” must be considered. Second, the extent to which patients for whom surgery is lacking despite its appropriateness must be assessed. Currently, “there is no evidence that either supports or refutes a racial difference in the proportion of patients, for whom it is an appropriate therapy, who actually receive carotid endarterectomy.” Third, the area of physician and patient decision making must be addressed. As the authors state, “Issues here relate to prior knowledge, patient-physician communication about the disease and treatment options, and patient preferences in the face of ‘complete information.’ It may be that black patients are not fully informed of the options. It is possible that physicians, unconsciously or otherwise, convey through words, tone, or body language less enthusiasm for surgery when discussing this option with black patients because of a belief in lower efficacy of the surgery for blacks or for other, as yet unclear, reasons.” The authors conclude that “whatever the policy response, it is clearly important to explore fully the decision-making process, including the patient-physician interaction during discussions of treatment options that involve invasive procedures.”