This study, which used clinically detailed data from a large population-based cohort study, adds to our knowledge about the extent and reasons for disparities in outcomes and use of procedures to prevent stroke in a several important areas. First, we found that both Blacks and Hispanics had higher rates of death and stroke after CEA (compared to Whites). Prior studies have shown inconsistent effects of race on outcomes of CEA, with about half reporting worse outcomes among Blacks (predominantly higher in-hospital mortality)13-17
and half finding no differences compared to Whites.18-23
Our data extends the finding of worse surgical outcomes in Blacks to the key clinical outcome of 30 day death or stroke--the main composite endpoint in the trials and national guidelines. The only two large prior studies that had clinically detailed data on outcomes found no Black-White differences in 30 day death or stroke.21, 22
Their focus on a single site22
or a Veterans Affairs population21
may explain the difference from our results which were based on a more generalizable statewide Medicare population.
Our finding that Hispanics had the highest rates of perioperative death and stroke after CEA is new. Since most prior work relied on administrative databases, they lacked the ability to accurately examine Hispanics as a separate subgroup. Trivedi et al. found a borderline excess of in-hospital deaths among Hispanics having CEA.16
In the Veterans Affairs National Surgical Quality Improvement Program study, Hispanics overall did not have worse outcomes, though the subgroup of Hispanics operated on for TIA had higher rates of death or stroke (compared to Whites).21
The reasons for the disparities in outcomes were multifactorial, were not just due to higher rates of symptomatic carotid disease among minorties, and appeared to differ in Blacks v. Hispanics. Among Blacks, the higher risk of complications attenuated to a borderline finding after procedure-specific risk adjustment indicating that differences in presurgical neurological acuity, disability, and comorbidity accounts for much, but not all of the Black-White disparity in outcomes. Further adjustments for surgeon and hospital experience further reduced the disparity suggesting that worse outcomes in Blacks are partly due to less experienced providers caring for them.
Among Hispanics, in-depth adjustment for patient, surgeon and hospital factors diminished the excess risk modestly, but Hispanics still had nearly double the risk-adjusted odds of death or stroke in the final multivariable model. This is a novel finding. Whether Hispanics had worse outcomes due to differences in other unmeasured factors related to pre-surgical patient risk, intra- or post-operative quality of care, or other more subtle surgeon, hospital, or community level influences is unknown and will require further investigation.
Contrary to what others have reported,24
the proportion of minority surgical patients at a given hospital did not influence the risk of CEA complications in either in minority or White patients. This suggests that, at least with regard to CEA, perioperative outcomes are largely driven by the individual patient’s pre-surgical risk and the skill and experience of the specific physician performing the operation, not the composition of the hospital’s patient population.
While the literature is consistent about underuse of CEA among minorities, this is the first study to examine racial and ethnic differences in overuse of CEA. Blacks and Hispanics had higher rates of inappropriate surgery, with Hispanics having the highest rates of overuse. The predominant reason for the higher rates of inappropriate surgery among minorities was that a larger proportion of them operated on for asymptomatic disease had high comorbidity. Why more minorities with asymptomatic disease and high comorbidity were selected for surgery is hard to understand and was unexpected.
Gender did not confound or explain the relationship between race/ethnicity and outcomes in either subgroup, stratified, or multivariate analyses. This is consistent with our previous report of no overall significant difference in perioperative outcomes between men and women in NYCAS.32
The literature examining the effects of gender on surgical complications of CEA is vast and has mixed findings.37, 38
Many studies, including several using similar large population-based, community practice cohorts, also reported no sex differences in perioperative death or stroke.15,23,38, 39
However, the asymptomatic RCTs found a non-significant trend suggesting a gender differential, 8, 10
and the symptomatic trials reported significantly higher surgical event rates among women.7, 9, 40
The current study had several strengths. It is the first to our knowledge to examine the step-wise impact of patient, surgeon and hospital factors as a way of understanding racial/ethnic disparities in clinically confirmed outcomes of CEA in a large, community setting with procedure specific risk-adjustment and validated measures of inappropriate care.
These strengths should be viewed in the context of a few limitations. Because NYCAS only contains data on patients who had CEA, we do not have any information about upstream decision making that would explain why certain patients were not recommended for or did not consent to surgery. Nor do we know why minorities undergoing CEA had more symptomatic disease, greater neurologic acuity, and greater comorbidity. Whether this is due to higher burden of cerebrovascular and other chronic diseases in minority elders or bias in perceived benefits and harms of CEA is unknown. Nor do we know why Non-Whites were more likely to be operated on by low volume surgeons or hospitals, even in the context of them being more likely to have surgery in teaching hospitals and large cities where high volume surgeons and centers are more readily available. Race and ethnicity were ascertained from physician clinical notes not self-report—though such determinations, while not perfect, should be more accurate than relying on claims data. Finally, while these data reflects practice in 1998-1999, operative techniques, perioperative management, and outcomes for CEA have been consistent over the intervening period, and there is little reason to believe that the association between race/ethnicity and clinical and provider risk factors would change considerably over time.
Our results have several policy implications. First, they highlight that efforts to measure and understand disparities (including disparities report cards) will need to try to control for patient, physician, and hospital level factors. Second, surgeon characteristics (volume, board specialty, and years in practice) appeared to be more important provider factors explaining disparities in outcomes than hospital volume ones. Most initiatives to improve surgical outcomes most often promote selective referral to high volume hospitals.41
In the case of CEA, our data suggest that the optimal policy strategy for reducing disparities would be to selectively refer minorities to high volume, experienced surgeons, something that is even harder to do than steering patients to high volume hospitals. Third, our findings reveal that lower overall rates of procedures in minorities that drive underuse
do not necessarily translate into lower rates of overuse
. The few other studies that examined this balance found more underuse of coronary revascularization42, 43
and renal transplantation44
among Blacks compared to Whites, but also less overuse of these procedures. In the case of CEA, minorities have more underuse and more overuse.
Taken together, our findings reveal the ‘worst of all worlds’--CEA is underused, overused and results in worse clinical outcomes for minorities. Because the reasons for such disparities in the quality and outcomes of CEA care are complex and appear to be operating at the patient, physician, and hospital level, strategies for reducing these inequities will be challenging and need to target multiple factors that influence patient selection and surgical referral patterns. From a research perspective, our approach suggests that studies relying solely on administrative data may be unable to adjust for important patient, surgeon and hospital level variables that contribute to disparities in clinical outcomes. Finally, from a clinical standpoint, more evidence-based decision aides are needed to help physicians and patients more appropriately weigh the potential risks and benefits of CEA for a given individual and better inform the surgeon and hospital referral decision.