title: Validity of international classification of disease codes to identify ischemic stroke and intracranial hemorrhage among individuals with associated diagnosis of atrial fibrillation.
abstract: BACKGROUND
  Because of its association with death and disability, stroke is a focus of outcomes in atrial fibrillation (AF) research. International Classification of Disease-Ninth Revision (ICD-9) edition codes are commonly used to identify stroke in research, particularly in large administrative data. We sought to assess the validity of ICD-9 codes in stroke case ascertainment and for AF across 3 institutions.
  
  
  RESULTS
  Participating centers included Boston Medical Center (safety net hospital), Geisinger Health System (rural Pennsylvania), and the University of Alabama (academic center in the southeastern stroke belt). ICD-9 codes for ischemic stroke (433-434, 436) and intracranial hemorrhage (430-432) identified 1812 stroke cases with an associated code for AF (427.31) from 2006 to 2010. Cases were vetted through chart review with final adjudication by a stroke neurologist. Review considered 94.2% of ICD-9 identified stroke cases valid with decreased accuracy for concurrent AF diagnosis (82.28%) and stroke attributable to AF (72.8%). Among events with "without infarction" modifiers, 7.2% were valid strokes. ICD-9 stroke code accuracy did not differ by stroke type or site. Stroke code 434 displayed higher accuracy than 433 (94.4% versus 85.2%; P<0.01), and primary stroke codes were more accurate than nonprimary codes (97.2% versus 83.7%; P<0.0001).
  
  
  CONCLUSIONS
  Using ICD-9 stroke and AF codes to identify patients with stroke plus AF resulted in inaccuracies. Given the expanded financial and policy implications of patient-oriented research, conclusions derived solely from administrative data without validation of outcome events should be interpreted with caution.
authors.affiliation: From the Department of Clinical and Administrative Sciences, Notre Dame of Maryland University School of Pharmacy, Baltimore (J.L.T.); Department of Neurology, University of Alabama at Birmingham (C.D., N.A.L.); Department of Medicine, Boston University Medical Center, MA (L.H., E.M.H.); Department of Biostatistics (Y.T.) and Date Coordinating Center (E.K.Q), Boston University School of Public Health, Boston, MA; and Department of Cardiology, Geisinger Health System, Danville, PA (K.B.F., P.B.B) jthigpen@ndm.edu.
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Thigpen
authors.affiliation: From the Department of Clinical and Administrative Sciences, Notre Dame of Maryland University School of Pharmacy, Baltimore (J.L.T.); Department of Neurology, University of Alabama at Birmingham (C.D., N.A.L.); Department of Medicine, Boston University Medical Center, MA (L.H., E.M.H.); Department of Biostatistics (Y.T.) and Date Coordinating Center (E.K.Q), Boston University School of Public Health, Boston, MA; and Department of Cardiology, Geisinger Health System, Danville, PA (K.B.F., P.B.B).
authors.forename: Chrisly
authors.initials: C
authors.lastname: Dillon
authors.affiliation: From the Department of Clinical and Administrative Sciences, Notre Dame of Maryland University School of Pharmacy, Baltimore (J.L.T.); Department of Neurology, University of Alabama at Birmingham (C.D., N.A.L.); Department of Medicine, Boston University Medical Center, MA (L.H., E.M.H.); Department of Biostatistics (Y.T.) and Date Coordinating Center (E.K.Q), Boston University School of Public Health, Boston, MA; and Department of Cardiology, Geisinger Health System, Danville, PA (K.B.F., P.B.B).
authors.forename: Kristen B
authors.initials: KB
authors.lastname: Forster
authors.affiliation: From the Department of Clinical and Administrative Sciences, Notre Dame of Maryland University School of Pharmacy, Baltimore (J.L.T.); Department of Neurology, University of Alabama at Birmingham (C.D., N.A.L.); Department of Medicine, Boston University Medical Center, MA (L.H., E.M.H.); Department of Biostatistics (Y.T.) and Date Coordinating Center (E.K.Q), Boston University School of Public Health, Boston, MA; and Department of Cardiology, Geisinger Health System, Danville, PA (K.B.F., P.B.B).
authors.forename: Lori
authors.initials: L
authors.lastname: Henault
authors.affiliation: From the Department of Clinical and Administrative Sciences, Notre Dame of Maryland University School of Pharmacy, Baltimore (J.L.T.); Department of Neurology, University of Alabama at Birmingham (C.D., N.A.L.); Department of Medicine, Boston University Medical Center, MA (L.H., E.M.H.); Department of Biostatistics (Y.T.) and Date Coordinating Center (E.K.Q), Boston University School of Public Health, Boston, MA; and Department of Cardiology, Geisinger Health System, Danville, PA (K.B.F., P.B.B).
authors.forename: Emily K
authors.initials: EK
authors.lastname: Quinn
authors.affiliation: From the Department of Clinical and Administrative Sciences, Notre Dame of Maryland University School of Pharmacy, Baltimore (J.L.T.); Department of Neurology, University of Alabama at Birmingham (C.D., N.A.L.); Department of Medicine, Boston University Medical Center, MA (L.H., E.M.H.); Department of Biostatistics (Y.T.) and Date Coordinating Center (E.K.Q), Boston University School of Public Health, Boston, MA; and Department of Cardiology, Geisinger Health System, Danville, PA (K.B.F., P.B.B).
authors.forename: Yorghos
authors.initials: Y
authors.lastname: Tripodis
authors.affiliation: From the Department of Clinical and Administrative Sciences, Notre Dame of Maryland University School of Pharmacy, Baltimore (J.L.T.); Department of Neurology, University of Alabama at Birmingham (C.D., N.A.L.); Department of Medicine, Boston University Medical Center, MA (L.H., E.M.H.); Department of Biostatistics (Y.T.) and Date Coordinating Center (E.K.Q), Boston University School of Public Health, Boston, MA; and Department of Cardiology, Geisinger Health System, Danville, PA (K.B.F., P.B.B).
authors.forename: Peter B
authors.initials: PB
authors.lastname: Berger
authors.affiliation: From the Department of Clinical and Administrative Sciences, Notre Dame of Maryland University School of Pharmacy, Baltimore (J.L.T.); Department of Neurology, University of Alabama at Birmingham (C.D., N.A.L.); Department of Medicine, Boston University Medical Center, MA (L.H., E.M.H.); Department of Biostatistics (Y.T.) and Date Coordinating Center (E.K.Q), Boston University School of Public Health, Boston, MA; and Department of Cardiology, Geisinger Health System, Danville, PA (K.B.F., P.B.B).
authors.forename: Elaine M
authors.initials: EM
authors.lastname: Hylek
authors.affiliation: From the Department of Clinical and Administrative Sciences, Notre Dame of Maryland University School of Pharmacy, Baltimore (J.L.T.); Department of Neurology, University of Alabama at Birmingham (C.D., N.A.L.); Department of Medicine, Boston University Medical Center, MA (L.H., E.M.H.); Department of Biostatistics (Y.T.) and Date Coordinating Center (E.K.Q), Boston University School of Public Health, Boston, MA; and Department of Cardiology, Geisinger Health System, Danville, PA (K.B.F., P.B.B).
authors.forename: Nita A
authors.initials: NA
authors.lastname: Limdi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001281:Atrial Fibrillation / Q000145:classification / Q000175:diagnosis* / Q000453:epidemiology; D002545:Brain Ischemia / Q000145:classification / Q000175:diagnosis* / Q000453:epidemiology; D057225:Data Mining / Q000379:methods*; D016208:Databases, Factual; D005260:Female; D006801:Humans; D038801:International Classification of Diseases; D020300:Intracranial Hemorrhages / Q000145:classification / Q000175:diagnosis* / Q000453:epidemiology; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D020521:Stroke / Q000145:classification / Q000175:diagnosis* / Q000453:epidemiology; D014481:United States / Q000453:epidemiology
keywords: International Classification of Disease codes; atrial fibrillation; intracranial hemorrhages; stroke