title: Developing a large electronic primary care database (Doctors' Independent Network) for research.
abstract: OBJECTIVE
  Primary care databases form a unique source of population-based clinical information on the prevalence and management of diagnosed disorders. Historically such databases have lacked individual level socio-economic markers. We describe the development of the Doctors' Independent Network (DIN) database for epidemiological and health services research. DIN includes a socio-economic marker (ACORN) based on postcode linkage at individual patient level. The validity of DIN is assessed against the General Practice Research Database (GPRD).
  
  
  METHODS
  External validity is assessed by comparing the demographic structure and prevalence rates for treated ischemic heart disease (IHD) and treated hay fever with those from the GPRD. We assess the utility of a socio-economic measure (ACORN) based on postcode-linkage at individual patient level by examining the trend in prevalence rates of IHD and hay fever by ACORN index.
  
  
  RESULTS
  142 practices providing high quality data were selected, with 1827361 fully registered patients contributing data between 1992 and 2001, representing an identical age-sex structure to that for England & Wales and GPRD. Regionally adjusted prevalence of treated IHD (7.29 and 5.37%, respectively for men and women aged 35+ in 1998) in DIN was highly comparable to GPRD (7.27 and 5.42%). In DIN, the odds ratio of IHD was 1.37 (95% CI 1.30-1.44) in subjects living in "striving" compared to "thriving" areas. The prevalence of treated hay fever prevalence was similar across databases, with inverse associations seen with ACORN in DIN (higher rates in "thriving" areas).
  
  
  CONCLUSIONS
  DIN provides comparable period prevalence rates to GPRD for two common conditions, with social trends as expected. Primary care databases such as these have the potential to replace the decennial national morbidity surveys carried out in UK general practices, with DIN having the important advantage of including a socio-economic index.
authors.affiliation: Department of Community Health Sciences, St George's Hospital Medical School, Cranmer Terrace, London SW17 0RE, UK. sgj450@sghms.ac.uk
authors.forename: Iain M
authors.initials: IM
authors.lastname: Carey
authors.forename: Derek G
authors.initials: DG
authors.lastname: Cook
authors.forename: Stephen
authors.initials: S
authors.lastname: De Wilde
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Bremner
authors.forename: Nicky
authors.initials: N
authors.lastname: Richards
authors.forename: Steve
authors.initials: S
authors.lastname: Caine
authors.forename: David P
authors.initials: DP
authors.lastname: Strachan
authors.forename: Sean R
authors.initials: SR
authors.lastname: Hilton
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D003625:Data Collection; D019992:Databases as Topic; D005260:Female; D006302:Health Services Research / Q000458:organization & administration*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000453:epidemiology; D010820:Physicians; D011320:Primary Health Care; D006255:Rhinitis, Allergic, Seasonal / Q000453:epidemiology; D012923:Social Class; D006113:United Kingdom / Q000453:epidemiology