(Harvard Medical School: Boston) -- Researchers at Harvard Medical School (HMA) and Massachusetts General Hospital have found wide disparities among four common measures of hospitalwide mortality rates, with competing methods yielding both higher and lower-than-expected rates for the same Massachusetts hospitals during the same year.

The findings, published Dec. 23, 2010, in a special article in the The New England Journal of Medicine, stoke a simmering debate over the value of hospitalwide mortality rates as a yardstick for health care quality. The measure, which compares a hospital’s actual patient death rate to statistical predictions, is reported publicly in countries including England, Canada, and Denmark, but some hospitals and policy experts have questioned its value due to the complexity and variability of diagnoses.

“It’s troubling that four different methods for calculating hospital mortality rates as a measure of quality should yield such different results,” says lead author David M. Shahian, HMS professor of surgery at Massachusetts General Hospital. “Measurement theory—not to mention plain common sense—suggests there is a problem.”

The potential of performance evaluation to improve both the quality and cost of health care has fueled interest in provider “report cards,” including mandates by state and federal law.

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