The impact of ICD-9 revascularization procedure codes on estimates of racial disparities in ischemic stroke

J Stroke Cerebrovasc Dis. 2014 Nov-Dec;23(10):2681-2686. doi: 10.1016/j.jstrokecerebrovasdis.2014.06.008. Epub 2014 Sep 26.


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.

Keywords: Administrative coding data; ischemic stroke; racial disparities; recurrence.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Brain Ischemia / classification*
  • Brain Ischemia / diagnosis
  • Brain Ischemia / surgery
  • Cerebral Revascularization / methods
  • Cerebral Revascularization / statistics & numerical data*
  • Female
  • Hospitalization / statistics & numerical data*
  • Humans
  • Incidence
  • International Classification of Diseases
  • Male
  • Middle Aged
  • Patient Discharge / statistics & numerical data
  • Racism*
  • Risk Factors
  • Stroke / classification*
  • Stroke / diagnosis
  • Stroke / surgery