Data content


We have organised THIN data into the following seven categories:

1. Demographics

  • Date patient registered at practice
  • Date patient left practice
  • Patient registration status
  • Year of birth
  • Gender
    Patients residing at the same address or members of the same family linked if at the same practice using a household identifier number


THIN Data does not include the following:

  • Name
  • Exact address or postcode
  • Exact date of birth (year can be given)
  • NHS number


2. Diagnoses

All conditions and symptoms are recorded electronically during each consultation with the GP/nurse and patient. This builds the patient medical histories.

Medical conditions are recorded using the Read Clinical Classification version 2.

Information on referrals to secondary care, including the specialty of the secondary care service, is available in THIN.

Secondary care information and other related information received by the practice is entered retrospectively, including:

  • Details on hospital admissions
  • Discharge medication and diagnosis
  • Outpatient consultation diagnosis
  • Investigation and treatment outcomes

    THIN data have been now linked with Hospital Episode Statistics (HES) data to provide additional information on secondary care in England.

    3. Prescribing

Prescriptions can be issued by the GP or the nurse. The GP/nurse will issue prescriptions to the patient by computer so all prescribing is logged into the system automatically.

The prescribing recorded in the computer logs the drug prescribed using a drug dictionary, which automatically creates therapy records for THIN.

Acute treatments and medicines for a chronic condition can be temporally linked with a symptom or diagnosis although this is not comprehensive in THIN.

The GP/nurse may summarise details of prescriptions from ongoing outpatient specialist care or over-the-counter drugs, but the degree of information depends on its direct relevance to the patient.

4. Additional Health Information

As well as GP consultations and details from other health care professionals, THIN Data contains information on lifestyle and health factors such as smoking and alcohol intake.

Tests and laboratory results are also accessible. More than 75% of THIN practices are now electronically linked to pathology laboratories and will receive test results electronically. This makes it easier for the practice to store results in the patient’s electronic record.

5. Free Text Comments

A key element of THIN data is commentary from the GP entered into free text fields. This can sometimes contain confidential or identifying information so THIN checks and ensures these comments have been pseudonymised.

6. Socioeconomic data from THIN

THIN also supplies data from other sources linked to the patient’s postcode (zip code equivalent) whilst maintaining confidentiality.

The majority of patients in THIN Data are linked to postcode-based socioeconomic, ethnicity and environmental indicators.

The methodology used to make this link allows THIN Data to be linked to other postcode level indicators. The data are based on the patient’s postcode so that individual socioeconomic data are available in the form of the Townsend score quintile, an established socioeconomic score indicator.

7. Links to external data

THIN data linked together with Hospital Episodes Statistics data (secondary care data covering inpatient and outpatient episodes of care) in England, are now available.

If you already use the THIN database and would like to access the additional HES linked records please contact us for more information.


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