Comparing hospital performance within and across countries: an illustrative study of coronary artery bypass graft surgery in England and Spain

OBJECTIVE: To assess the feasibility, strengths and weaknesses of using administrative data to compare hospital performance across countries, using mortality after coronary artery bypass graft (CABG) surgery as an illustrative example. METHODS: Country specific and pooled models using individual-level data and logistic regression methods assess individual hospital performance using funnel plots accounting for multiple testing. Outcomes are adjusted for age, sex, comorbidities and indicators of patient severity. Data includes patients from all publicly funded hospitals delivering CABG surgery in England and Spain. Inpatient hospital-level standardized mortality rates within 30 days of CABG surgery are calculated for 83 999 CABG patients between 2007 and 2009. RESULTS: Unadjusted national mortality rates are 5% in Spain and 2.3% in England. Country-specific models identified similar patterns of excess mortality 'alerts' and 'alarms' in hospitals in Spain or England. Pooling data from both countries identifies larger numbers of alerts and alarms in Spanish hospitals, and risk-adjustment increased the already large national mortality difference. This was reduced but not eliminated by accounting for lower volume in Spanish hospitals. CONCLUSION: Cross-national comparisons potentially add value by providing international performance benchmarks. Hospital-level analysis across countries can illuminate differences in hospital performance, which might not be identified using country-specific data or incomplete registry data, and can test hypotheses that may explain national differences. Difficulties of making data comparable between countries, however, compound the usual within-country measurement problems.