title: Factors influencing the detection of early CT signs of cerebral ischemia: an internet-based, international multiobserver study.
abstract: OBJECTIVE
  Early CT signs of cerebral ischemia are subtle. Little is known of which factors influence the detection of infarct signs. We compared neuroradiologists' scan readings with those of other specialists involved in the care of stroke patients.
  
  
  METHODS
  We used the Internet to show 63 CT scans, all acquired <6 hours after stroke and representing different patient ages, times to scanning, stroke severity, and early CT signs of ischemia to physicians involved in stroke care. They completed a structured scan interpretation proforma over the Internet. We compared the detection of early ischemic signs stratified by severity and the effect of prior stroke between different specialties.
  
  
  RESULTS
  Among 207 observers, neuroradiologists saw significantly more of "any early ischemic changes" than did stroke physicians, general radiologists, geriatricians, or neurologists (all P<0.0001), predominantly due to neuroradiologists' greater detection of "mild" hypoattenuation or swelling. Detection of "severe" hypoattenuation or swelling, and hyperattenuated arteries did not differ between specialties. Old infarcts impaired recognition of early ischemic signs. Non-neuroradiologists did not "over-call" signs. Years of scan-reading experience did not account for these differences, but neuroradiologists took, on average, 30 seconds longer to read each scan than did most other specialists (P<0.0001).
  
  
  CONCLUSIONS
  Non-neuroradiologists should realize that they are unlikely to over-call signs, that old infarcts may distract them from seeing early ischemic signs, and read stroke CT scans more slowly, as these factors may help them perform more like neuroradiologists.
authors.affiliation: Division of Clinical Neurosciences, University of Edinburgh, Western General Hospital, Edinburgh, UK. Joanna.wardlaw@ed.ac.uk
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Wardlaw
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Farrall
authors.forename: David
authors.initials: D
authors.lastname: Perry
authors.forename: Rudiger
authors.initials: R
authors.lastname: von Kummer
authors.forename: Orell
authors.initials: O
authors.lastname: Mielke
authors.forename: Thierry
authors.initials: T
authors.lastname: Moulin
authors.forename: Alfonso
authors.initials: A
authors.lastname: Ciccone
authors.forename: Michael
authors.initials: M
authors.lastname: Hill
mesh_terms: D000368:Aged; D001921:Brain / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D002545:Brain Ischemia / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D003951:Diagnostic Errors / Q000517:prevention & control / Q000706:statistics & numerical data*; D042241:Early Diagnosis; D006801:Humans; D007391:International Cooperation; D020407:Internet / Q000706:statistics & numerical data*; D009462:Neurology / Q000706:statistics & numerical data; D015588:Observer Variation; D011237:Predictive Value of Tests; D011871:Radiology / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D020521:Stroke / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000592:standards / Q000706:statistics & numerical data*