–Patient volume has been found to be only a mild indicator of hospital performance in the treatment of three common conditions, according to a new study in the current edition of the New England Journal of Medicine.
A team of researchers led by Joseph Ross, MD, MHS, Assistant Professor of Geriatrics and Palliative Medicine and of Medicine at Mount Sinai School of Medicine, examined mortality rates at low, medium and high volume hospitals for patients treated for acute myocardial infarction (heart attack), heart failure, and pneumonia. The researchers found that while hospitals with higher patient volume performed marginally better than lower volume hospitals, performance peaked at relatively low patient volumes and treating more patients beyond those levels did not result in even further reduced mortality rates.
“Though higher patient volume has been associated with lower hospital mortality for numerous surgical conditions and medical procedures, it has been unclear whether hospital patient volume may be a similar indicator for acute medical care,” said Dr. Ross. “Our findings highlight that, unlike with surgery and procedures, patient volume is a weak indicator of clinical outcomes for acute medical conditions.
“Several organizations have suggested that hospital volume be used by patients to identify hospitals that provide the best quality of care. However, in the study there was a wide range of performance among small hospitals and substantial overlap of performance between small, medium and large hospitals,” said Dr. Ross. “Moreover, among hospitals with greater volumes, a threshold was reached where greater annual volume was not predicted to be associated with lower mortality. Future research should be focused on identifying strategies used at higher quality hospitals to improve the quality of care.”
The researchers analyzed Medicare administrative claims data for all fee-for-service beneficiaries hospitalized between 2004 and 2006 in U.S. acute-care hospitals for acute myocardial infarction, heart failure, or pneumonia. Using hierarchical logistic models for each condition, they then estimated the change in patient odds of 30-day mortality associated with increasing annual hospital volume by 100 cases. Analyses were adjusted for patient risk factors and hospital characteristics.
In the study period there were 734,972 hospitalizations for acute myocardial infarction in 4,128 hospitals; 1,324,287 for heart failure in 4,679 hospitals; and 1,418,252 for pneumonia in 4,673 hospitals. For acute myocardial infarction, once hospital annual volume reached 610 patients increasing hospital volume by 100 cases no longer significantly lowered a patient’s odds of death. The volume-threshold for heart failure hospitalizations was 500 and for pneumonia was 210 hospitalizations.
Dr. Ross said, “This study shows that health policies such as regionalization that are intended to universally increase hospital volume in an effort to lower mortality rates should not be expected to have uniform benefits. Large hospitals may have the financial capacity to justify employing clinical teams whose sole responsibility is to manage commonly treated conditions through disease management and discharge programs. Small hospitals may need additional support to ensure that effective strategies are available at all hospitals.”
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