Linkage of National Congenital Heart Disease Audit data to hospital, critical care and mortality national datasets to enable research focused on quality improvement
Authors: Pujol Ferran Espuny , Pagel Christina , Brown Katherine L. , Doidge James C. , Feltbower Richard G. , Franklin Rodney C. , Gonzalez-Izquierdo Arturo , Gould Doug W. , Norman Lee J. , Stickley John , Taylor Julie A. , Crowe Sonya 
Published: November 2021

AbstractObjectivesTo 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.DesignBespoke 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.SettingNational 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.ParticipantsPatients with any CHD procedure recorded in NCHDA between April 2000 and March 2017 from public hospitals.Primary and secondary outcome measuresPrimary 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.ResultsThere 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.ConclusionsWe 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.Strengths and limitations of this studyStrengthsWe linked five national established, high quality, datasets using bespoke methods for the pre-processing of identifiers and establishing matches to maximise linkageIn our final dataset, data consistency has been checked at patient level using year and month of birth, postcodes, and diagnosis codes, and also clinically sense-checked at spell level for spells containing congenital heart procedures.We created meaningful spells of care for each patient in the dataset covering inpatient and outpatient interactions with secondary and tertiary care, covering up to 20 years of life of patients with congenital heart disease (CHD), representing an important step to understanding patient care for people with CHD.LimitationsData completeness, quality and availability were worse in earlier years, meaning that linkage was poorer for earlier eras.We do not yet have data on hospital care for patients outside England or on longer term adult follow-up for patients whose full CHD history is captured, since most cardiac procedures start in early live – the national CHD audit (NCHDA) started on April 2000.