title: The validity of the extension-rotation test as a clinical screening procedure before neck manipulation: a secondary analysis.
abstract: OBJECTIVE
  To determine the validity of the neck extension-rotation test as a clinical screening procedure to detect decreased vertebrobasilar blood flow that might be associated with dizziness.
  
  
  METHODS
  Secondary analysis of a clinical screening test.
  
  
  METHODS
  Twelve subjects with dizziness reproduced by the extension-rotation test and 30 healthy control subjects had Doppler ultrasonography examination of their vertebral arteries with the neck extended and rotated. Vascular impedance to blood flow was measured and the presence of signs and symptoms of vertebrobasilar ischemia was recorded.
  
  
  RESULTS
  Cut-off points for validity estimates were derived through the percentile and Gaussian methods using impedance to blood flow as the standard. The sensitivity of the extension-rotation test for increased impedance to blood flow was 0%, regardless of the selected cut-off point. The specificity rates for the left vertebral artery were 71% and 67% for the percentile and Gaussian methods, respectively. The extension-rotation test was more specific on the right side, with a rate varying from 90% with the percentile method to 86% with the Gaussian technique. The positive predictive value of the test was 0% and its negative predictive value ranged from 63% to 97%.
  
  
  CONCLUSIONS
  We were unable to demonstrate that the extension-rotation test is a valid clinical screening procedure to detect decreased blood flow in the vertebral artery. The value of this test for screening patients at risk of stroke after cervical manipulation is questionable.
authors.affiliation: Department of Orthopaedics, Royal University Hospital, Saskatoon, Saskatchewan, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Côté
authors.forename: B G
authors.initials: BG
authors.lastname: Kreitz
authors.forename: J D
authors.initials: JD
authors.lastname: Cassidy
authors.forename: H
authors.initials: H
authors.lastname: Thiel
mesh_terms: D000328:Adult; D002684:Chiropractic / Q000379:methods*; D004244:Dizziness / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009333:Neck; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D014715:Vertebrobasilar Insufficiency / Q000150:complications / Q000175:diagnosis*