Two scientific studies released today question the reliability and merit of using patient volume at hospitals as an indicator of the likelihood of a good outcome in heart surgery or in care of low-birth-weight infants. In a study by the Duke Clinical Research Institute, hospital procedural volume was "only modestly associated" with death rates for coronary artery bypass graft surgery. Referring to the highest-volume hospitals would have averted 50 deaths in a study of 267,000 heart-bypass procedures in 2000 and 2001, less than 1% of the 7,110 deaths that occurred. The study found wide variability in risk-adjusted mortality among hospitals of similar volume. It also identified many low-volume hospitals with low death rates and some high-volume centers with higher-than-expected mortality. "Hospital volume had generally poor predictive accuracy as a means of identifying hospitals with significantly better or worse (bypass) mortality rates," wrote Eric Peterson, lead researcher on the study, which will be published in tomorrow's Journal of the American Medical Association. Using volume as the sole basis of referrals would unfairly divert cases from nearly half of low-volume medical centers with outcomes equal to or better than overall death rates, he said.
Meanwhile, a study by Rand Corp., to be published in the same issue of JAMA, found that hospitals treating the highest number of infants under three pounds at birth were not always the facilities with the lowest rate of infant deaths. The study at 332 hospitals over 5 years found that basing a referral system on volume standards would have saved an estimated 11 lives annually among the group, while basing referrals on historical mortality rates would have saved 115 lives -- a 10-fold difference. -- by John Morrissey