title: The impact of ICD-9 revascularization procedure codes on estimates of racial disparities in ischemic stroke.
abstract: BACKGROUND
  The use of International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9) diagnostic codes can identify racial disparities in ischemic stroke hospitalizations; however, inclusion of revascularization procedure codes as acute stroke events may affect the magnitude of the risk difference. This study assesses the impact of excluding revascularization procedure codes in the ICD-9 definition of ischemic stroke, compared with the traditional inclusive definition, on racial disparity estimates for stroke incidence and recurrence.
  
  
  METHODS
  Patients discharged with a diagnosis of ischemic stroke (ICD-9 codes 433.00-434.91 and 436) were identified from a statewide inpatient discharge database from 2010 to 2012. Race-age specific disparity estimates of stroke incidence and recurrence and 1-year cumulative recurrent stroke rates were compared between the routinely used traditional classification and a modified classification of stroke that excluded primary ICD-9 cerebral revascularization procedures codes (38.12, 00.61, and 00.63).
  
  
  RESULTS
  The traditional classification identified 7878 stroke hospitalizations, whereas the modified classification resulted in 18% fewer hospitalizations (n = 6444). The age-specific black to white rate ratios were significantly higher in the modified than in the traditional classification for stroke incidence (rate ratio, 1.50; 95% confidence interval [CI], 1.43-1.58 vs. rate ratio, 1.24; 95% CI, 1.18-1.30, respectively). In whites, the 1-year cumulative recurrence rate was significantly reduced by 46% (45-64 years) and 49% (≥ 65 years) in the modified classification, largely explained by a higher rate of cerebral revascularization procedures among whites. There were nonsignificant reductions of 14% (45-64 years) and 19% (≥ 65 years) among blacks.
  
  
  CONCLUSIONS
  Including cerebral revascularization procedure codes overestimates hospitalization rates for ischemic stroke and significantly underestimates the racial disparity estimates in stroke incidence and recurrence.
authors.affiliation: Department of Neuroscience, Medical University of South Carolina, Charleston, South Carolina; Department of Pediatrics, Medical University of South Carolina, Charleston, South Carolina. Electronic address: boan@musc.edu.
authors.forename: Andrea D
authors.initials: AD
authors.lastname: Boan
authors.affiliation: Department of Neuroscience, Medical University of South Carolina, Charleston, South Carolina.
authors.forename: Jenifer H
authors.initials: JH
authors.lastname: Voeks
authors.affiliation: Department of Neuroscience, Medical University of South Carolina, Charleston, South Carolina.
authors.forename: Wuwei Wayne
authors.initials: WW
authors.lastname: Feng
authors.affiliation: Department of Neuroscience, Medical University of South Carolina, Charleston, South Carolina.
authors.forename: David L
authors.initials: DL
authors.lastname: Bachman
authors.affiliation: Department of Neuroscience, Medical University of South Carolina, Charleston, South Carolina; Division of Emergency Medicine, Medical University of South Carolina, Charleston, South Carolina.
authors.forename: Edward C
authors.initials: EC
authors.lastname: Jauch
authors.affiliation: Department of Neuroscience, Medical University of South Carolina, Charleston, South Carolina.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Adams
authors.affiliation: Department of Neuroscience, Medical University of South Carolina, Charleston, South Carolina.
authors.forename: Bruce
authors.initials: B
authors.lastname: Ovbiagele
authors.affiliation: Department of Neuroscience, Medical University of South Carolina, Charleston, South Carolina.
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Lackland
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002545:Brain Ischemia / Q000145:classification* / Q000175:diagnosis / Q000601:surgery; D002548:Cerebral Revascularization / Q000379:methods / Q000706:statistics & numerical data*; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D038801:International Classification of Diseases; D008297:Male; D008875:Middle Aged; D010351:Patient Discharge / Q000706:statistics & numerical data; D063505:Racism; D012307:Risk Factors; D020521:Stroke / Q000145:classification* / Q000175:diagnosis / Q000601:surgery
keywords: Administrative coding data; ischemic stroke; racial disparities; recurrence