The Dartmouth Atlas of Health is once again throwing a harsh spotlight on McAllen, Texas.

This time the Mexican border town has the highest rate of leg amputations in the nation, a new report released recently showed. McAllen’s rate was ten times the rate of Provo, Utah, which had the lowest rate of leg amputations among the Medicare eligible population. The national average was one-third of McAllen’s rate.

McAllen became notorious earlier this year because of a New Yorker article by Dr. Atul Gawande, which showed how overutilization of services in that city gave it the highest rate of Medicare spending in the country. Though a subsequent Medicare Payments Advisory Commission report concluded that adjusting for prices and other factors would rank McAllen’s Medicare spending rate as comparable to any number of southern and southwestern cities with inordinately high rates, the town’s reputation never recovered.

So I was curious about the latest uproar over amputation rates, which was reported by Kaiser Health News and given wider coverage on National Public Radio’s blog. Were McAllen doctors really whacking away at the limbs of elderly Medicare beneficiaries at an unnecessarily high rate? The implications were just too horrible to contemplate.

It turns out that the data in that one section of the report had not been adjusted for underlying disease patterns. The primary cause of leg amputations among elderly Medicare beneficiaries is poorly controlled diabetes and associated peripheral vascular disease. These conditions are disproportionately high in heavily Hispanic communities like McAllen.

It’s curious that the Dartmouth Atlas investigators didn’t adjust for diabetes. In the other sections of the report, which was written to show that access to primary care physicians did not necessarily lead to patients receiving better preventive care, they made those adjustments.

They looked at the the number of diabetic patients receiving annual blood sugar tests. They looked at the number of diabetic patients receiving annual eye exams. Both are key tests for primary care physicians if they want to keep track of their diabetic patients’ adherence to the medications that can control diabetes and peripheral vascular disease.

“The idea that primary care is going to solve our quality problems is just simply wrong,” said journalist Shannon Brownlee, who co-wrote the report. “The environment — poverty, smoking, exercise, diet — are the biggest determinants. Giving a hemoglobin A1C test once a year made no difference. Neither does having an eye exam.”

But when the researchers looked at amputations, the outcome of poor control, they didn’t looking at the rates among diabetic Medicare beneficiaies, they looked at the rate among all Medicare beneficiaries.

Now, it is true that McAllen was the outlier on the overall rate of amputations. And it is also true that the rate of primary care visits in McAllen was in the upper half of communities in the U.S. (Remember, the report’s larger theme was that primary care didn’t necessarily lead to good preventive care.) But until one knows the amputation rate among diabetic Medicare beneficiaries in McAllen and its relationship to primary care visits, it’s hard to draw conclusions about what it says about McAllen.

Merrill Goozner is senior correspondent for The Fiscal Times and blogs on health care and other issues at GoozNews.com.

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