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Using GPRD for Primary Care Research

Using GPRD for Primary Care Research


Observational data representative of the UK population

Because of the comprehensive population coverage of the primary health care system in the UK, GPRD is an excellent resource for conducting robust medical and epidemiological research. GPRD has full records for over 3.6 million currently registered patients and over 13 million patients in total. These data are collected from around 430 practices and cover 4.6% of the UK population. The patient population captured in the database is broadly representative of the demographic breakdown of the UK population (Table 1: by Region and Gender, Table 2: by Age and Gender).

Primary care research using GPRD

The large sample size and representativeness of the data mean there is considerable statistical power for cohort and case-control studies and to draw robust conclusions on disease incidence, risk factors, exposure effects, treatment patterns and health outcomes. GPRD is particularly suited to long-term cohort studies because it contains over 35 million patient years of high quality validated data, with over 15 years of records for individual patients. The duration of follow up time for patients in FF-GPRD is shown in figure 1.

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Richness of the data

Data in GPRD are available at the individual patient level. Although no patient or practice identifiable data are collected, each patient has an encrypted unique number which allows their records to be linked over time. For each patient GPRD collects and makes available:

  • Demographic information including gender, year of birth and practice location (to Strategic Health Authority level).
  • All clinical information including diagnoses, symptoms, procedures, and medical history.
  • All prescriptions issued and repeat prescription schedules with dosage instructions.
  • Referrals to secondary care including hospital speciality, urgency, and nature of the referral (e.g. day case).
  • Immunisation details including status, stage, and type, route of administration, reason and batch number.
  • Tests results including qualitative and quantitative test result values and also normal ranges for the laboratory.
  • Lifestyle information including BMI, height, weight and details on smoking and alcohol consumption.
  • Patient registration details which are used to generate start and end dates of longitudinal electronic recording for person-time calculations.
  • Appointment and staff details including duration of consultation and gender and role of the health professional concerned.
  • Adverse drug reaction details including certainty and severity assessments.
  • Additional clinical details which provide supplementary information on a variety of situations (e.g. contraception, child health surveillance, ante- and post-natal care) and conditions (e.g. asthma, diabetes).
  • Anonymised free text information which can be used to validate diagnoses or patient management.

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Scientific approval for GPRD data

Anyone interested in conducting a study using GPRD data is required to gain approval from the MHRA's Independent Scientific Advisory Committee for MHRA database research (ISAC). This involves submitting a brief outline of the study protocol to ISAC for review.

For further details on ISAC please click Here.

ISAC application form

Data collection and validation

The GPRD Group is the only provider of updated GPRD data - we collect, validate, update and maintain the quality of the records in the database. We actively maintain good relationships with contributing practices to ensure up-to-dateness of data collections.