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Black patients with critical limb ischemia are more likely than their white counterparts to undergo amputation instead of revascularization, according to a large registry study published online March 20, 2013, ahead of print in JAMA Surgery. This pattern is sharpened by treatment at hospitals very experienced in revascularization and by higher socioeconomic status, undercutting conventional explanations for the racial disparity.

Tyler S. Durazzo, MD, and colleagues from Yale University School of Medicine (New Haven, CT), looked at 350,992 patients with critical lower limb ischemia in the Nationwide Inpatient Sample who underwent either amputation (37.5%) or surgical revascularization (62.5%) between 2002 and 2008. Patient race or ethnicity was recorded as white, black, or Hispanic.

Race an Independent Predictor of Amputation

Black patients were more likely to receive amputation than were white patients or, to a lesser degree, Hispanic patients (56.4% vs. 34.5% and 48.2%, respectively; P < 0.001 for both comparisons).

Regression analysis controlling for significant baseline variables showed that, after presentation with gangrene and prior attempt at revascularization, black race was the strongest independent predictor of amputation:

• Gangrene (OR 11.22; 95% CI 10.8-11.56)
• Prior attempt at revascularization (OR 2.63; 95% CI 2.47-2.81)
• Black race (OR 1.77; 95% CI 1.72-1.84)

Other positive predictors included relying on Medicare or Medicaid coverage, chronic renal failure, and diabetes.

Conversely, white race, having private insurance, residing in the wealthiest zip codes, having chronic obstructive pulmonary disease, chronic heart disease or hypertension, and being cared for at a teaching hospital all favored revascularization.

Almost two-thirds of patients of both races presented to hospitals with the greatest capacity for revascularization, based on the overall volume of such procedures performed. Of note, the disparity in management of black vs. white patients was higher at those hospitals than centers with lower revascularization volume.

In addition, although overall the likelihood of receiving revascularization vs. amputation rose with the mean income of the zip code in which patients lived, that relationship was reversed for blacks. The odds ratio for amputation among blacks compared with whites rose from 2.04 (95% CI 1.95-2.14) for the poorest quartile of zip codes to 2.45 (95% CI 2.27-2.65) for the wealthiest quartile of zip codes.

Access to Care Not the Explanation

The findings show that racial disparities in the treatment of critical limb ischemia “cannot be explained solely on the basis of differences in access to care,” the authors say. However, they observe, “race-specific factors that exist following hospital admission may play a significant role in the treatment and outcomes. . . . [Indeed,] unintentional or unconscious bias in medical decision making . . . cannot be ruled out as contributing to the disparity.”

In an accompanying editorial, Karl A. Illig, MD, of the University of South Florida Health, Morsani College of Medicine (Tampa, FL), points to another possible explanation: a genetic basis for the behavior of peripheral vascular disease.

He argues that there are biological differences between broadly defined ethnic groups, such that one patient may have “disease that is more amenable to bypass when symptomatic, while the other has a greater chance of presenting with anatomically nonreconstructable occlusion—all because of genetic factors.”

While this argument may be “politically dangerous,” Dr. Illig says, “if we ignore it, we run the risk of doing just what we are trying to avoid—giving one group of patients inferior care because we have not recognized the true cause of the problem.”

A Minority Position on Minorities

In a telephone interview with TCTMD, Vincent L. Rowe, MD, of the University of Southern California (Los Angeles, CA), aligned himself with this assessment.

Many critics, especially among African-Americans, have looked for inequities in the system such as barriers to access, delays to presentation, and bias on the part of physicians, he observed. “I’m in a bit of a minority about this issue,” Dr. Rowe said. “I think the evidence documenting a difference in treatment is true, I just think the [reasons for] the differences are in the patients.”

Dr. Rowe cited his own research (Rowe VL. Vasc Endovascular Surg. 2007;41:397-401) in which all study patients were on a level playing field in terms of socioeconomic background, insurance, and stage of disease, and yet black patients had worse outcomes. Likewise, the current paper points to the patient as the source of the disparity in treatment for minorities, Dr. Rowe suggested, because it rules out the influence of access to quality care.

Acknowledging that his belief treads on sensitive ground, Dr. Rowe, who identified himself as African-American, stressed that “once you find out that a disease behaves differently in a certain racial group, it doesn’t mean that they are in any way inferior, it just means that you have to do a better job of screening and focus on this group because they do the worst with the disease.”

Ultimately, longitudinal studies are needed to clarify the impact of race on the natural history of the disease and the response to surgery, he said, noting that the results could suggest either more or less aggressive treatment.

Betting on DNA Differences

“You have to look at DNA and perhaps inflammatory markers,” Dr, Rowe said, “because if you look only at [the presence of] other vascular problems like carotid disease or aneurysms, there is no difference based on race.”

Dr. Rowe reported that he is seeking funding for such a study. A formidable challenge, he noted, is that most data on ethnicity, including those from the Nationwide Inpatient Sample, rely on self-reporting, while the DNA of ‘black’ patients from North America may be quite different from that of ‘black’ patients from Africa or the Caribbean.

The study authors leave open the question of why there are racial differences in management of critical limb ischemia. But, they say, finding the explanation “is critical to better understanding our health care system and maintaining approaches that are consistently fair and equitable.”

Study Details

The racial and ethnic groups differed in multiple baseline characteristics. In terms of comorbidities, black and Hispanic patients were more likely to have diabetes and chronic renal failure, while white patients more commonly had hypertension, congestive heart failure, and chronic obstructive pulmonary disease (all P < 0.001). In addition, black and Hispanic patients were more likely to present with gangrene, whereas white patients were more likely to present with ulcers or rest pain (all P < 0.001).

2. Illig KA. Why do nonwhite patients undergo amputation more commonly than white patients? JAMA Surg. 2013;Epub ahead of print.

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