title: Validity and completeness of colorectal cancer diagnoses in a primary care database in the United Kingdom.
abstract: OBJECTIVE
  To validate the recorded diagnoses of colorectal cancer (CRC) and identify false negatives in The Health Improvement Network (THIN) primary care database.
  
  
  METHODS
  We conducted a validation study of incident CRC cases in THIN among patients aged 40-89 years from 2000-2011. CRC Read code entries (N = 3805) were verified by manual review of patients' electronic medical records (EMRs) including free-text comments. Incident CRC cases in THIN ascertained following manual review were validated against two data sources deemed gold standards: (i) questionnaires sent to primary care practitioners (PCPs; for a random sample of 100 potential CRC cases), and (ii) Hospital Episode Statistics (HES) among linked practices. False negatives in THIN were identified by searching for International Classification of Diseases-10 codes related to CRC in HES.
  
  
  RESULTS
  Of 3805 CRC cases identified in THIN via Read codes, 3033 patients (80.0%) were considered definite cases after manual review of EMRs. The positive predictive value (PPV) of CRC Read codes was 86.0% after removing patients identified from THIN via a Read code for 'fast track referral for suspected CRC'. The response rate from PCPs was 87.0% (n = 87), and the PPV of CRC in THIN was 100% based on PCP questionnaires. Using HES, the PPV for CRC in THIN was 97.9% (556/568), and false negative rate was 6.1% (36/592).
  
  
  CONCLUSIONS
  CRC diagnostic Read codes in THIN have a high PPV, which is increased further following manual review of free-text comments. The false negative rate of CRC diagnoses in THIN is low.
authors.affiliation: Spanish Centre for Pharmacoepidemiologic Research (CEIFE), Madrid, Spain.
authors.forename: Lucía
authors.initials: L
authors.lastname: Cea Soriano
authors.affiliation: Global Epidemiology, Bayer Pharma AG, Berlin, Germany.
authors.forename: Montse
authors.initials: M
authors.lastname: Soriano-Gabarró
authors.affiliation: Spanish Centre for Pharmacoepidemiologic Research (CEIFE), Madrid, Spain.
authors.forename: Luis A
authors.initials: LA
authors.lastname: García Rodríguez
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000453:epidemiology; D016208:Databases, Factual / Q000706:statistics & numerical data*; D057286:Electronic Health Records / Q000706:statistics & numerical data*; D005188:False Negative Reactions; D006801:Humans; D038801:International Classification of Diseases; D008875:Middle Aged; D011237:Predictive Value of Tests; D011320:Primary Health Care / Q000706:statistics & numerical data*; D011795:Surveys and Questionnaires; D006113:United Kingdom
keywords: colorectal cancer; database; pharmacoepidemiology; validation studies