Pilot study linking primary care records to Census, cardiovascular hospitalization and mortality data in Scotland: Feasibility, utility and potential

Background: There are substantial ethnic variations in the risk of cardiovascular disease (CVD)-related hospitalization and mortality in Scotland. We piloted extracting and linking primary care risk factors to Scottish Census and health data, to test the feasibility of further investigating these variations. Methods: Data extracted from 10 general practices were linked at individual level to Census and hospitalization/death records. Linkage rates, reasons for non-linkage and completeness of primary care data were examined. CVD relative risks were calculated, adjusting for age, socioeconomic status and primary care-derived risk factors. Results: Practice enrolment and data extraction proved challenging. Primary care records for 52 975 (55.2%) people were linked to Census data. Completeness and validity of risk variables were similar across ethnic groups. A total of 48 325 (91.2%) records had a valid smoking status recorded and 2900 (5.5%) people had a primary care record of diabetes. Ethnic-specific adjusted estimates of CVD risk were plausible and consistent with previous work. Conclusions: Risk factor data extracted from primary care were of good quality and successfully linked to national Census records. Given further methodological refinement, this method illustrates the potential value of linkage using national primary care datasets to contribute to public health surveillance and research.