Cross-provincial use of cardiac services: the importance of data-sharing for clinical registries and outcomes research.

BACKGROUND The structure of the Canadian health care system lends itself to health services and health outcomes research. It is possible to track hospital admissions and discharges, physician billings and prescriptions using administrative databases. In addition, several provinces have developed registries that provide detailed clinical and procedural information. Using the unique personal health numbers assigned to all Canadian residents, linkage between administrative databases and population-based clinical registries provides important information regarding the use of health services and health outcomes. OBJECTIVE To determine the extent of cross-border (British Columbia-Alberta border) use of cardiac services by British Columbia residents. METHODS Population rates of cardiac procedures were calculated using two prospective clinical registries (British Columbia Cardiac Registries and Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease [APPROACH]), as well as administrative databases (the British Columbia Ministry of Health's hospitalization and Medical Services Plan databases). RESULTS Analyses using only British Columbia data suggest low cardiac procedure rates for patients living in eastern British Columbia. By accessing APPROACH data, it was determined that more than 80% of British Columbia cardiac patients living along the British Columbia-Alberta border access procedural services in Alberta. CONCLUSIONS While residents of eastern British Columbia appear to have reduced access to cardiac services when data from British Columbia are analyzed in isolation, they are actually accessing care in Alberta. Analyses based solely on single province data sources will underestimate cardiac procedures rates.