The Health Improvement Network
The Health Improvement Network (THIN) is a large database of anonymised electronic medical records collected at Primary Care clinics throughout the UK. The THIN database is managed by IMS Health Real World Evidence in collaboration with In Practice Systems UK.
The THIN database is similar in structure and content to the Clinical Practice Research Datalink (CPRD, previously known as GPRD), which is now managed by the United Kingdom Medicines and Healthcare products Regulatory Agency (MHRA).
Between 1994 and 2002, EPIC (UK), a not-for-profit company, held a non-exclusive licence to use GPRD for research benefitting public health. On the expiry of that licence, THIN was developed by EPIC as an alternative to the GPRD, and a substantial number of primary care practitioners now contribute data to both resources.
In 2005 EPIC was acquired by Cegedim, a global technology and services company specialising in the healthcare field. EPIC become part of the Cegedim Strategic Data - Medical Research UK (CSD-MR UK) division within Cegedim, which can also provide researchers with access to similar data from 9 million patients in Europe and other parts of the world. In April 2015, CSD-MR UK was acquired by IMS Health and renamed IMS Health Real World Evidence.
THIN data are made available under more permissive terms than other similar resources (such as the CPRD, which does not allow for-profit use by private companies), but access is subject to ethical approval by an independent Scientific Review Committee.
Data collection commenced in January 2003, using information extracted from Vision, a widely used general practice management software package developed by In Practice Systems, a company also owned by Cegedim SA.
Clinical data in THIN are catalogued using Read codes, a comprehensive and searchable classification scheme for medical conditions, symptoms and important background information. This system is complemented by a set of Additional Health Data (AHD) codes which provide a standardised system for the recording of a wide variety of clinical measurements, and by drug codes which identify prescribed medications.
Since 2004, the UK Quality and Outcomes Framework, a performance-related pay scheme for primary care practitioners, has effectively mandated the use of computer systems (such as Vision) to maintain patient medical records, and has imposed standardised recording methods for a wide range of important medical conditions. In addition, practitioners contributing data to THIN receive training to ensure consistent recording of important clinical outcomes and indicators including:
- Coronary heart disease
- Diabetes mellitus
- Leg ulcers
- Heart failure
- Warfarin use
- Lithium use
- Use of hormonal contraception
- Pernicious anaemia
- Rheumatoid arthritis
- Secondary stroke prevention
- Lower back pain
- Mental health
- Smoking status
THIN is an important resource in the fields of epidemiology, drug safety and health outcomes research, providing an inexpensive means to study the causes of disease and effectiveness of interventions in a large, representative population.
-  About us - IMS Health Real World Evidence UK
- The Health Improvement Network - US National Cancer Institute
- IMS Health Completes Acquisition of Cegedim’s CRM and Strategic Data Businesses
- IMS Health: Ethics
- UCL THIN database user group
- List of peer-reviewed publications using THIN Cegedim Strategic Data - Medical Research UK
- Lewis et al., “Validation Studies of the Health Improvement Network (THIN) Database for Pharmacoepidemiology Research.” 
- Bourke, Dattani, and Robinson, “Feasibility Study and Methodology to Create a Quality-evaluated Database of Primary Care Data.”