They show that up to 50% of all heart attack cases are missed using just one data source.
These findings may be relevant to other common conditions, such as stroke, and support the wider use of linked multiple record sources by clinicians, policy makers and researchers, say the authors.
Electronic health records are increasingly used to measure health outcomes, and for research, but records from one part of the health service (e.g. primary care) may not capture health events occurring in other parts of the health system (e.g. hospital care).