Estimating the potential impact of regionalizing health care delivery based on volume standards versus risk-adjusted mortality rate.

OBJECTIVE To examine whether basing regionalization on risk-adjusted mortality would lead to better population outcomes than basing regionalization on procedure volume. DATA SOURCE We used secondary data from the California State Inpatient Database obtained from the Healthcare Costs and Utilization Project. STUDY DESIGN A population-based retrospective cohort study of 243 thousand patients who underwent either abdominal aortic aneurysm surgery, coronary artery bypass surgery or coronary angioplasty between 1998 and 2000 in California. Four regionalization strategies were compared: (i) selective referral to high-quality hospitals; (ii) selective referral to high-volume hospitals; (iii) selective avoidance of low-quality hospitals; (iv) selective avoidance of low-volume hospitals. PRINCIPAL FINDINGS Selective referral to high volume centers would be only moderately effective (2-20% relative reduction in mortality) and extremely disruptive (70-99% reduction in the number of hospitals treating these conditions). Selective referral to high quality centers was estimated to result in dramatic reduction in mortality (50%) but would also be highly disruptive with greater than 80% of the patients re-directed to high quality centers. Selective avoidance of low volume hospitals would not improve mortality, whereas selective avoidance of low quality hospitals was estimated to result in a small improvement in overall mortality (2-6%) while causing relatively minor disruptions in patient referral patterns. CONCLUSION Efforts to use volume standards as the basis for evidence-based hospital referrals should be re-evaluated by all stake-holders before promoting further efforts to regionalize health care delivery using volume cutoffs.