Surgeon and hospital volume as quality indicators for CABG in Taiwan: examining hazard to mortality and accounting for unobserved heterogeneity.

OBJECTIVE To investigate whether provider volume has an impact on the hazard of mortality for coronary artery bypass grafting (CABG) patients in Taiwan. DATA SOURCES/STUDY SETTING Multiple sources of linked data from the National Health Insurance Program in Taiwan. STUDY DESIGN The linked data were used to identify 27,463 patients who underwent CABG without concomitant angioplasty or valve procedures and the surgeon and hospital volumes. Generalized estimating equations and hazard models were estimated to assess the impact of volume on mortality. The hazard modeling technique used accounts for bias stemming from unobserved heterogeneity. PRINCIPAL FINDINGS Both surgeon and hospital volume quartiles are inversely related to the hazard of mortality after CABG. Patients whose surgeon is in the three higher volume quartiles have lower 1-, 3-, 6-, and 12-month mortality after CABG, while only those having their procedure performed at the highest quartile of volume hospitals have lower mortality outcomes. CONCLUSIONS Mortality outcomes are related to provider CABG volume in Taiwan. Unobserved heterogeneity is a concern in the volume-outcome relationship; after accounting for it, surgeon volume effects on short-term mortality are large. Using models controlling for unobserved heterogeneity and examining longer term mortality may still differentiate provider quality by volume.