Linkage of National Congenital Heart Disease Audit data to hospital, critical care and mortality national datasets to enable research focused on quality improvement

Objectives To link five national datasets (three registries, two administrative) and create longitudinal health care trajectories for patients with congenital heart disease (CHD), describing the quality and the summary statistics of the linked dataset. Design Bespoke linkage of record-level patient identifiers across five national datasets. Generation of spells of care defined as periods of time-overlapping events across the datasets. Setting National congenital heart disease audit (NCHDA) procedures in public (NHS) hospitals in England and Wales, paediatric and adult intensive care datasets (PICANet and ICNARC-CMP), administrative hospital episodes (HES inpatient, outpatient, A&E), and mortality registry data. Participants Patients with any CHD procedure recorded in NCHDA between April 2000 and March 2017 from public hospitals. Primary and secondary outcome measures Primary outcomes: Number of linked records, number of unique patients and number of generated spells of care (e.g. inpatient stays, outpatient appointments). Secondary outcomes: Quality and completeness of linkage. Results There were 143,862 records in NCHDA relating to 96,041 unique patients. We identified 65,797 linked PICANet patient admissions, 4,664 linked ICNARC-CMP admissions, and over 6 million linked HES episodes of health care (1.1M Inpatient, 4.7M Outpatient). The 96,041 unique patients had 4,908,153 spells of care comprising 6,481,600 records after quality checks. Considering only years where datasets overlapped, 95.6% surgical procedure records were linked to a corresponding HES record, 93.9% paediatric (cardiac) surgery procedure records were linked to a corresponding PICANet admission, and 76.8% adult surgery procedure records were linked to a corresponding ICNARC-CMP record. Conclusions We successfully linked four national datasets to the core dataset of all CHD procedures performed between 2000 and 2017. This will enable a much richer analysis of longitudinal patient journeys and outcomes. We hope that our detailed description of the linkage process will be useful to others looking to link national datasets to address important research priorities.