title: Accuracy of administrative databases in identifying patients with hypertension.
abstract: BACKGROUND
  Traditionally, the determination of the occurrence of hypertension in patients has relied on costly and time-consuming survey methods that do not allow patients to be followed over time.
  
  
  OBJECTIVE
  To determine the accuracy of using administrative claims data to identify rates of hypertension in a large population living in a single-payer health care system.
  
  
  METHODS
  Various definitions for hypertension using administrative claims databases were compared with 2 other reference standards: (1) data obtained from a random sample of primary care physician offices throughout the province, and (2) self-reported survey data from a national census.
  
  
  RESULTS
  A case-definition algorithm employing 2 outpatient physician billing claims for hypertension over a 3-year period had a sensitivity of 73% (95% confidence interval [CI] 69%-77%), a specificity of 95% (CI 93%-96%), a positive predictive value of 87% (CI 84%-90%), and a negative predictive value of 88% (CI 86%-90%) for detecting hypertensive adults compared with physician-assigned diagnoses. Compared with self-reported survey data, the algorithm had a sensitivity of 64% (CI 63%-66%), a specificity of 94%(CI 93%-94%), a positive predictive value of 77% (76%-78%), and negative predictive value of 89% (CI 88%-89%). When this algorithm was applied to the entire province of Ontario, the age- and sex-standardized prevalence of hypertension in adults older than 35 years increased from 20% in 1994 to 29% in 2002.
  
  
  CONCLUSIONS
  It is possible to use administrative data to accurately identify from a population sample those patients who have been diagnosed with hypertension. Given that administrative data are already routinely collected, their use is likely to be substantially less expensive compared with serial cross-sectional or cohort studies for surveillance of hypertension occurrence and outcomes over time in a large population.
authors.forename: Karen
authors.initials: K
authors.lastname: Tu
authors.forename: Norman Rc
authors.initials: NR
authors.lastname: Campbell
authors.forename: Zhong-Liang
authors.initials: ZL
authors.lastname: Chen
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Cauch-Dudek
authors.forename: Finlay A
authors.initials: FA
authors.lastname: McAlister