Table 2.

Linked electronic health record sources in CALIBER: types of data, coding system used and data recording details

Sources	Types of data	Coding system	When and by whom data is coded?
Primary care: CPRD and other sources	Longitudinal primary care data Diagnoses and symptoms irrespective of hospitalization, drug prescriptions, vaccinations, blood test results, risk factors	Data recorded using the Read clinical terminology system, version 3 contains ∼99 000 codes	Data recoded by the general practitioner in real time during the consultation Hospital discharge letters coded by a practice administrator
Social deprivation: ONS	Small area patient social deprivation data	Index of Multiple Deprivation (2007) and Townsend score	Derived from multiple national administrative data sets
Disease registry: MINAP	National registry of Acute Coronary Syndrome admissions Phenotype (ST Elevation Myocardial Infarction, Non-ST Elevation Myocardial Infarction, Unstable Angina), severity and treatment data	In all, 120 fields most with multiple response categories, as defined by the MINAP steering group	Recorded usually by audit nurse, days or weeks after admission, by abstracting data from hospital records
Secondary care: HES	National data warehouse of hospitalizations recorded for administrative purposes Inpatient, outpatient, emergency, critical care and maternity admissionsa Operations and surgical procedures	Up to 20 primary and secondary discharge diagnoses recorded using ICD-10 Up to 24 codes using the Office of Population, Censuses and Surveys Classification of Surgical Operations and Procedures and used for operations The 4th revision (OPCS-4) contains ∼10 000 codes	Recorded by non-clinical trained coders based on the discharge summary weeks after discharge
Mortality: ONS	National census of all deaths Primary and underlying cause of death	The primary, underlying and up to 14 secondary causes of death are recorded using ICD-10	Doctor (general practitioner or hospital) completes death certificate with cause of death. ICD codes added by trained non-clinical coders

^aEmergency, critical care and maternity data not included in CALIBER for now.