Practice makes perfect: a volume-outcome study of hospital patients with HIV disease

There is considerable evidence that patients with HIV fare better in hospitals that treat more HIV-positive patients. Yet, it is possible that much of this benefit is attributable to the care provided by physicians who treat high volumes of HIV-positive patients. This study examines the relation between 2 measures of volume (the number of HIV-positive patients treated in a hospital and the number of HIV-positive patients treated by the attending physician) and the probability of dying in the hospital.

This study uses discharge data from 43,325 patients hospitalized with HIV disease in 5 states (Colorado, Maryland, New Jersey, New York, and Washington State) in 2002. These data were obtained from the Agency for Healthcare Research and Quality's Healthcare Cost and Utilization Project State Inpatient Databases.

Volume-outcome studies have demonstrated an inverse relation between the number of HIV-positive patients treated at a hospital and the mortality rate for these patients. Yet, the most current of these studies is based on data more than a decade old, and none of these account for the volume of HIV-positive patients treated by the physician. This study uses multivariate logistic regression analyses to estimate the impact of hospital and physician volume on patient mortality.

This study found that when measures of physician and hospital volume are included in a regression equation explaining patient mortality, only the variable measuring physician volume remains statistically significant. Moreover, when a variable is defined for each patient based on the quartile rankings of the patient's hospital volume and the patient's physician volume, the quartile ranking of physician volume is a better predictor of survival than the quartile ranking of hospital volume.

These findings suggest that the volume of patients treated by the attending physician is the key measure of volume associated with the survival of hospitalized HIV-positive patients.