title: Case misclassification in studies of spinal manipulation and arterial dissection.
abstract: BACKGROUND
  Spinal manipulation has been associated with cervical arterial dissection and stroke but a causal relationship has been questioned by population-based studies. Earlier studies identified cases using International Classification of Diseases Ninth Revision (ICD-9) codes specific to anatomic stroke location rather than stroke etiology. We hypothesize that case misclassification occurred in these previous studies and an underestimation of the strength of the association. We also predicted that case misclassification would differ by patient age.
  
  
  METHODS
  We identified cases in the Veterans Health Administration database using the same strategy as the prior studies. The electronic medical record was then screened for the word "dissection." The presence of atraumatic dissection was determined by medical record review by a neurologist.
  
  
  RESULTS
  Of 3690 patients found by ICD-9 codes over a 30-month period, 414 (11.2%) had confirmed cervical artery dissection with a positive predictive value of 10.5% (95% confidence interval [CI] 9.6%-11.5%). The positive predictive value was higher in patients less than 45 years of age vs 45 years of age or older (41% vs 9%, P < .001). We reanalyzed a previous study, which reported no association between spinal manipulation and cervical artery dissection (odds ratio [OR] = 1.12, 95% CI .77-1.63) and recalculated an odds ratio of 2.15 (95% CI .98-4.69). For patients less than 45 years of age, the OR was 6.91 (95% CI 2.59-13.74).
  
  
  CONCLUSIONS
  Prior studies grossly misclassified cases of cervical dissection and mistakenly dismissed a causal association with manipulation. Our study indicates that the OR for spinal manipulation exposure in cervical artery dissection is higher than previously reported.
authors.affiliation: Department of Neurology, Brigham and Women's Hospital and Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Xuemei
authors.initials: X
authors.lastname: Cai
authors.affiliation: Department of Neurology, Brigham and Women's Hospital and Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Ali
authors.initials: A
authors.lastname: Razmara
authors.affiliation: Tufts Clinical and Translational Science Institute (CTSI), Tufts University, Boston, Massachusetts; Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts.
authors.forename: Jessica K
authors.initials: JK
authors.lastname: Paulus
authors.affiliation: Tufts Clinical and Translational Science Institute (CTSI), Tufts University, Boston, Massachusetts.
authors.forename: Karen
authors.initials: K
authors.lastname: Switkowski
authors.affiliation: Department of Neurology, Tufts Medical Center, Boston, Massachusetts.
authors.forename: Pari J
authors.initials: PJ
authors.lastname: Fariborz
authors.affiliation: Harvard Medical School Division of General and Internal Medicine and Ariadne Labs, Boston, Massachusetts.
authors.forename: Sergey D
authors.initials: SD
authors.lastname: Goryachev
authors.affiliation: Harvard Medical School Division of General and Internal Medicine and Ariadne Labs, Boston, Massachusetts.
authors.forename: Leonard
authors.initials: L
authors.lastname: D'Avolio
authors.affiliation: Department of Neurology Tufts University School of Medicine.
authors.forename: Edward
authors.initials: E
authors.lastname: Feldmann
authors.affiliation: Department of Neurology, Tufts Medical Center, Boston, Massachusetts. Electronic address: dthaler@tuftsmedicalcenter.org.
authors.forename: David E
authors.initials: DE
authors.lastname: Thaler
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000473:pathology*; D057286:Electronic Health Records; D005260:Female; D006801:Humans; D038801:International Classification of Diseases / Q000592:standards; D008297:Male; D020393:Manipulation, Spinal / Q000145:classification* / Q000706:statistics & numerical data*; D008875:Middle Aged; D016017:Odds Ratio; D012307:Risk Factors; D020217:Vertebral Artery Dissection / Q000145:classification* / Q000453:epidemiology*
keywords: Stroke; risk factor; spinal manipulation; stroke prevention
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