Persons Diagnosed with COVID in England in the Clinical Practice Research Datalink (CPRD): A Cohort Description
Authors: Andersen Kathleen M. , McGrath Leah J. , Reimbaeva Maya , Mendes Diana , Nguyen Jennifer L. , Rai Kiran K. , Tritton Theo , Tsang Carmen , Malhotra Deepa , Yang Jingyan 
Published: March 2023

ABSTRACTObjectiveTo create case definitions for confirmed COVID diagnoses, COVID vaccination status, and three separate definitions of high risk of severe COVID, as well as to assess whether the implementation of these definitions in a cohort reflected the sociodemographic and clinical characteristics of COVID epidemiology in England.DesignRetrospective cohort studySettingElectronic healthcare records from primary care (Clinical Practice Research Datalink, or CPRD) linked to secondary care data (Hospital Episode Statistics, or HES) data covering 24% of the population in EnglandParticipants2,271,072 persons aged 1 year and older diagnosed with COVID in CPRD Aurum between August 1, 2020 through January 31, 2022.Main Outcome MeasuresAge, sex, and regional distribution of COVID cases and COVID vaccine doses received prior to diagnosis were assessed separately for the cohorts of cases identified in primary care and those hospitalized for COVID (primary diagnosis code of ICD-10 U07.1 “COVID-19”). Smoking status, body mass index and Charlson Comorbidity Index were compared for the two cohorts, as well as for three separate definitions of high risk of severe disease used in the United Kingdom (NHS Highest Risk, PANORAMIC trial eligibility, UK Health Security Agency Clinical Risk prioritization for vaccination).ResultsCompared to national estimates, CPRD case estimates underrepresented older adults in both the primary care (age 65-84: 6% in CPRD vs 9% nationally) and hospitalized (31% vs 40%) cohorts, and overrepresented people living in regions with the highest median wealth areas of England (20% primary care and 20% hospital admitted cases in South East, vs 15% nationally). The majority of non-hospitalized cases and all hospitalized cases had not completed primary series vaccination. In primary care, persons meeting high risk definitions were older, more often smokers, overweight or obese, and had higher Charlson Comorbidity Index score.ConclusionsCPRD primary care data is a robust real-world data source and can be used for some COVID research questions, however limitations of the data availability should be carefully considered. Included in this publication are supplemental files for atotal of over 28,000 codes to define each of three definitions of high risk of severe disease.SUMMARY BOXESWhat is already known on this topic?The UK Government publishes data on cases, hospital admissions and vaccinations related to COVID in England.There are at least three definitions of persons at high-risk of severe COVID in use in England.What this study addsOur study created case definitions for COVID diagnoses, COVID vaccination, and three separate definitions of high risk of severe COVID for use in the Clinical Practice Research Datalink (CPRD), a database covering 24% of England.The COVID population in the CPRD has a different age and regional distribution than national case reports, which future studies may need to consider.