Primary care electronic health records provide a rich source of information for inequalities research. However, the reliability and validity of the research derived from these records depend on the completeness and resolution of the codelists (ie, collections of medical terms/codes) used to identify populations of interest. The aim of this project was to develop comprehensive codelists for identifying people from ethnic minority groups, people with learning disabilities (LDs), people with severe mental illness (SMI) and people who are transgender.

We followed a three-stage process to define and extract relevant codelists. First, groups of interest were defined a priori. Next, relevant clinical codes, relating to the groups, were identified by searching Clinical Practice Research Datalink (CPRD) publications, codelist repositories and the CPRD Code Browser. Relevant codelists were extracted and merged according to group, and duplicates were removed. Finally, the remaining codes were reviewed by two general practitioners (GPs).

The curated codelists were compared using a representative sample in the UK. The frequencies of individuals identified using the curated codelists were assessed and compared with widely used alternative codelists.

Comprehensiveness was assessed in a representative CPRD population of 10 966 759 people.

After removal of duplicates and GP review, codelists were finalised with 325 unique codes for ethnicity, 558 for LD, 499 for SMI and 38 for transgender. Compared with comparator codelists, an additional 48 017 (76.6%), 52 953 (68.9%) and 508 (36.9%) people with LD, SMI or transgender code were identified. The proportions identified for ethnicity, meanwhile, were consistent with expectations for the UK (eg, 6.50% Asian, 2.66% black and 1.44% mixed).

The curated codelists are more sensitive than those widely used in practice and research. Discrepancies between national estimates and primary care records suggest potential record/retention issues. Resolving these requires further investigation and could lead to improved data quality for research.

An increasing number of teenagers and young adults (TYA) with chronic conditions and complex needs are transitioning from paediatric to adult services, including admission to intensive care units (ICUs). As these services are often ill-equipped to care for TYA, there is a risk of compromised care. Despite recent guidelines from the UK Paediatric Critical Care and Intensive Care Societies highlighting the importance and urgency of improving ICU transition, current recommendations are not evidence-based and established pathways for ICU transition remain limited.

This mixed-methods research study aims to generate evidence to underpin national policy on transition from paediatric to adult ICUs that will improve clinical care and patient experience. To do this, we will: (1) link and analyse UK national data (years 2017–2024) on paediatric and adult ICU admissions, hospital inpatient, outpatient and emergency care visits and survival status, to determine the clinical characteristics and healthcare resource utilisation from teenage years to early adulthood of people admitted to an ICU as a young person (admission aged 14 and 15), and how these relate to ICU admissions after age 16; (2) conduct semistructured interviews, online forums and surveys with TYA patients, carers and health professionals to understand their experience of transition in ICU services; and (3) synthesise these strands of evidence and use a structured process of stakeholder engagement to propose potential targeted improvements as appropriate.

This study was approved by the East of England - Cambridge South Research Ethics Committee on 1 August 2024 (research ethics committee number 24/EE/0108), and the Health Research Authority Confidentiality Advisory Group (CAG) on 7 October 2024 (CAG number 24/CAG/0068). Study results will be actively disseminated through peer-reviewed journals, conference presentations and accessible lay texts and graphic summaries for the use of charities and patients including those with learning disabilities and neurodevelopmental disorders.