title: Surgeon and hospital volume as quality indicators for CABG in Taiwan: examining hazard to mortality and accounting for unobserved heterogeneity.
abstract: OBJECTIVE
  To investigate whether provider volume has an impact on the hazard of mortality for coronary artery bypass grafting (CABG) patients in Taiwan.
  
  
  METHODS
  Multiple sources of linked data from the National Health Insurance Program in Taiwan.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
authors.affiliation: Department of Health Management and Policy, University of Iowa College of Public Health, 200 Hawkins Dr. E206, Iowa City, IA 52242, USA. jason-hockenberry@uiowa.edu
authors.forename: Jason M
authors.initials: JM
authors.lastname: Hockenberry
authors.forename: Hsien-Ming
authors.initials: HM
authors.lastname: Lien
authors.forename: Shin-Yi
authors.initials: SY
authors.lastname: Chou
mesh_terms: D000368:Aged; D016507:Cardiology Service, Hospital / Q000706:statistics & numerical data*; D001026:Coronary Artery Bypass / Q000401:mortality* / Q000639:trends; D005260:Female; D006302:Health Services Research; D006742:Hospital Bed Capacity / Q000706:statistics & numerical data; D017052:Hospital Mortality / Q000639:trends; D006801:Humans; D007344:Insurance Claim Reporting / Q000706:statistics & numerical data; D016015:Logistic Models; D008297:Male; D008498:Medical Record Linkage; D008875:Middle Aged; D009313:National Health Programs / Q000458:organization & administration; D017063:Outcome Assessment, Health Care; D010343:Patient Admission / Q000706:statistics & numerical data*; D016016:Proportional Hazards Models; D019984:Quality Indicators, Health Care / Q000458:organization & administration*; D020379:Risk Adjustment; D013624:Taiwan / Q000453:epidemiology