BACKGROUND: In the United Kingdom, hospital or cancer registry data can be linked to electronic medical records for a subset of general practices and years.
METHODS: We used Clinical Practice Research Datalink data (2004-2012) from patients treated for overactive bladder. We electronically identified provisional cases of 10 common cancers in General Practitioner Online Database data and validated them by medical profile review. In practices with linkage to Hospital Episodes Statistics and National Cancer Data Repository, for the period with data availability (2004-2010), we validated provisional cancer cases against Hospital Episodes Statistics or the National Cancer Data Repository. Linkage to these sources also let us identify additional cancer diagnoses in individuals without cancer diagnosis records in the General Practitioner Online Database.
RESULTS: Among 50,840 patients, 1,486 provisional cancer cases were identified in the General Practitioner Online Database for 2004-2012. Medical profile review confirmed 93% of 661 cases in non-linked practices (range, 100% of non-Hodgkin lymphomas and uterine cancer to 77% of skin melanomas) and 96% of 825 cases in linked practices (100% of kidney and uterine cancers to 92% of melanomas). In linked practices, during the period with available data from the General Practitioner Online Database, Hospital Episodes Statistics, and National Cancer Data Repository (2004- 2010), 720 cases were confirmed, of which 68% were identifiable in the General Practitioner Online Database (range, 90% of breast to 36% of kidney cancers).
CONCLUSIONS: Most cases of cancer identified electronically in the General Practitioner Online Database were confirmed. A substantial proportion of cases, especially of cancer types not typically managed by general practitioners, would be missed without Hospital Episodes Statistics and National Cancer Data Repository data (and are likely missed in non-linked practices).
