Validation of an electronic, population-based prescription database

BACKGROUND: The Drug Programs Information Network (DPIN), Manitoba's (Canada) new electronic prescription database, is a valuable data source for pharmacoepidemiologic research. Pharmacies are required to submit to the DPIN all prescriptions for Pharmacare, the province's drug insurance plan, but submission of prescriptions for social assistance recipients and treaty status Indians is discretionary. OBJECTIVE: The completeness of the DPIN prescription database was assessed to determine whether treaty status Indians and social assistance recipients were underrepresented. DESIGN: Prescriptions dispensed during March 13-17, 1995, in a stratified sample of Manitoba pharmacies were linked to DPIN by prescription number to determine the proportions submitted for Indian Affairs, Social Services, and Pharmacare recipients. Pharmacare records in the DPIN were compared with original pharmacy records to evaluate data accuracy. RESULTS: Of 2196 Indian Affairs and 1879 Social Services prescriptions dispensed in 58 pharmacies, a corresponding prescription was found in the DPIN for 79.7% (98% CI 78.0% to 81.4%) and 90.1% (98% CI 88.8% to 91.4%) of prescriptions, respectively. These proportions were significantly lower than the estimated proportion of Pharmacare prescriptions submitted (93%, 98% CI 92.4% to 93.6%). Ninety-two percent of 8012 DPIN Pharmacare prescriptions matched the original prescription on the drug name, quantity, and days' supply. CONCLUSIONS: This study established that the DPIN is a valid and reliable data source for studying prescription use among the majority of Manitoban residents. However, the DPIN database has differential validity and underrepresents prescriptions dispensed for the aboriginal population.