title: Identification of esophageal cancer in the General Practice Research Database.
abstract: BACKGROUND
  Studies based on the first appearance of a code for esophageal cancer in the General Practice Research Database (GPRD) have yielded conflicting results concerning the relationship between disease onset and prior bisphosphonate use. The literature on the timing of cancer code appearance in general practice records is scanty but suggests that there may be substantial error by comparison with actual dates of clinical onset.
  
  
  OBJECTIVE
  To assess the accuracy of codes for esophageal cancer in the GPRD and to determine whether it was possible to infer clinical date of onset.
  
  
  METHODS
  A reviewer adjudicated the records of women with codes for esophageal cancer from 1996 to 2008 by using chronological GPRD listings of codes for diagnoses, services, and tests. GPRD staff sought reviews by the general practices for 75 women whom the reviewer classified as having esophageal cancer and 25 classified as not having the condition.
  
  
  RESULTS
  Essentially all cases bearing a code for the condition had esophageal cancer. Where data were available to permit dating of clinical onset (75% of cases), the result agreed with the date recorded in the clinical record to within 60 days in 89% of cases. The remaining 25% of cases had little or no clinical information and could not be dated. Clinical onset preceded the first appearance of a cancer code by more than 6 months in 10% of cases.
  
  
  CONCLUSIONS
  The accurate timing of clinical onset and diagnosis in the GPRD, at least of esophageal cancer in women, may require the review of clinical records or future linkage to cancer registries.
authors.affiliation: World Health Information Science Consultants, LLC, Newton, MA 02466, USA. Alec.Walker@WHISCON.com
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Walker
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D059019:Clinical Coding / Q000706:statistics & numerical data*; D016208:Databases, Factual; D016021:Epidemiologic Studies; D004938:Esophageal Neoplasms / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology; D005260:Female; D041981:Gastrointestinal Tract / Q000473:pathology; D058006:General Practice / Q000706:statistics & numerical data*; D006801:Humans; D016347:Medical Records Systems, Computerized; D008875:Middle Aged; D015233:Models, Statistical; D011320:Primary Health Care / Q000706:statistics & numerical data*; D012042:Registries; D012189:Retrospective Studies; D012984:Software