title: Stroke: who's counting what?
abstract: BACKGROUND
  Patients with stroke are often selected for epidemiological reporting and research using ICD-9-CM (ICD-9) diagnostic codes. This study addresses the accuracy of these codes in identifying patients with stroke.
  
  
  METHODS
  A sample of 279 patients with new stroke and 392 non-stroke (no evidence of new stroke) patients were identified by medical record review from 11 Veterans Affairs Medical Centers. Administrative records containing ICD-9-CM diagnoses were matched with this sample. Coding sensitivity and specificity were determined using individual ICD-9 codes and two coding algorithms.
  
  
  RESULTS
  Significant variation was found in the accuracy of cerebrovascular ICD-9-CM codes in identifying patients diagnosed with stroke. Two coding algorithms were identified with the following performance statistics based on the sampled populations: 1) 91-percent sensitivity, 40-percent specificity; and 2) 54-percent sensitivity, 87-percent specificity.
  
  
  CONCLUSIONS
  Variability in identifying patients with stroke using ICD-9 codes has been reported in the literature and confirmed. Two coding algorithms for maximizing sensitivity or specificity are proposed. Caution is urged when using ICD-9-coded administrative data to identify patients with stroke.
authors.affiliation: Department of Veterans Affairs Medical Center, Kansas City, MO 64128, USA. dean.reker@med.va.gov
authors.forename: D M
authors.initials: DM
authors.lastname: Reker
authors.forename: B B
authors.initials: BB
authors.lastname: Hamilton
authors.forename: P W
authors.initials: PW
authors.lastname: Duncan
authors.forename: S C
authors.initials: SC
authors.lastname: Yeh
authors.forename: A
authors.initials: A
authors.lastname: Rosen
mesh_terms: D000465:Algorithms; D006801:Humans; D012680:Sensitivity and Specificity; D020521:Stroke / Q000145:classification* / Q000453:epidemiology*; D014481:United States / Q000453:epidemiology