Table 1.

Key details about the Clinical Practice Research Datalink

Counties participating	UK: England, Wales, Scotland and Nortdern Ireland
Who is included?	Patients registered at general practices that contribute data to CPRD, who have not dissented from secondary use of GP patient-identifiable data
What is recorded?	Demographics, diagnoses, symptoms, signs, prescriptions, referrals, immunisations, behavioural factors, tests
Period of data collection	1987 to present
	Average duration of follow-up 5.1 years
Funding source	CPRD has received funding from the MHRA, Wellcome Trust, Medical Research Council, NIHR Health Technology Assessment programme, Innovative Medicines Initiative, UK Department of Health, Technology Strategy Board, Seventh Framework Programme EU, and various universities, contract research organizations and pharmaceutical companies