Hospital Size and Volume Important

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Researchers from Mount Sinai School of Medicine reviewed hospital size and volume for three common medical conditions and found they were indeed important, but only to a point.

Dr Joseph Ross and colleagues found that patients with acute myocardial infarction (MI), heart failure, or pneumonia were less likely to die if admitted to hospitals with greater case volumes for those conditions.

The report appears in the March 25, 2010 issue of the New England Journal of Medicine. The researchers analyzed data from Medicare administrative claims data between 2004 and 2006 in acute care hospitals in the United States for acute myocardial infarction, heart failure, or pneumonia. This data was used to estimate the change in 30-day mortality for every 100-patient increase in annual case volumes for the three conditions after adjusting for hospital characteristics and patient risk features.

There were 734,972 hospitalizations for acute MI in 4128 hospitals, 1,324,287 for heart failure in 4679 hospitals, and 1,418,252 for pneumonia in 4673 hospitals. The researchers excluded the very lowest volume hospitals (10 or fewer cases over three years of observation) and patients discharged alive within one day of admission.

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An increased hospital volume was associated with reduced 30-day mortality for all conditions, but "at greater volumes, the marginal benefit became increasingly small," regardless of whether a hospital was a teaching hospital or featured cardiovascular revascularization, the group writes.

For acute MI, once the annual volume reached 610 patients (95% confidence interval [CI], 539 to 679), an increase in the hospital volume by 100 patients was no longer significantly associated with reduced odds of death.

The volume threshold was 500 patients (95% CI, 433 to 566) for heart failure and 210 patients (95% CI, 142 to 284) for pneumonia.

In an interview with heartwire, Dr. Ross notes "we found volume to be a weak surrogate for quality," lead author Dr Joseph S Ross, "The really interesting finding is that the relationship between volume and mortality is dynamic. It makes less and less difference to be a bigger and bigger hospital," he said. The analysis also showed lots of variance, in that some small hospitals had poor outcomes for the three conditions while others rivaled the best of the higher-volume centers. "And there were big hospitals that didn't do so well."

Source reference:
Ross JS, et al "Hospital volume and 30-day mortality for three common medical conditions" N Engl J Med 2010; 362: 1110-18.

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