Disease registries derived from Electronic Health Records (EHRs) are widely used for chronic disease management. We approached registries from the perspective of integrated care in a health neighbourhood, considering data quality issues such as semantic interoperability (consistency), accuracy, completeness and duplication. Our proposition is that a realist ontological approach is required to accurately identify patients in an EHR or data repository, assess data quality and fitness for use by the multidisciplinary integrated care team. We report on this approach with routinely collected data in a practice based research network in Australia.