title: Interreader reliability for a new classification of lumbar disk disease.
abstract: OBJECTIVE
  The nomenclature that divides disk herniations into protrusions and extrusions may increase the specificity of magnetic resonance (MR) imaging for clinically important lesions. Our goal was to determine this terminology's interreader reliability.
  
  
  METHODS
  Three readers who were unaware of patients' histories independently read MR images of 34 consecutive patients with back pain. Readers classified disks at the lowest three lumbar levels as normal, bulging, protruded, or extruded. Kappa and weighted kappa values were the primary measures of agreement.
  
  
  RESULTS
  Weighted kappa values showed fair-to-moderate agreement. Kappas for the dichotomous decision of extrusion present or absent were more variable, ranging from 0 to .78. Major disagreements (greater than a single category) occurred with 6.2% of all comparisons and in 10 of 34 volunteers; five involved extrusions.
  
  
  CONCLUSIONS
  Overall, readers achieved moderate agreement for this new nomenclature. However, agreement for the presence or absence of an extrusion was less reliable.
authors.affiliation: Department of Radiology, School of Medicine, University of Washington, Seattle 98195, USA.
authors.forename: J G
authors.initials: JG
authors.lastname: Jarvik
authors.forename: D R
authors.initials: DR
authors.lastname: Haynor
authors.forename: T D
authors.initials: TD
authors.lastname: Koepsell
authors.forename: A
authors.initials: A
authors.lastname: Bronstein
authors.forename: D
authors.initials: D
authors.lastname: Ashley
authors.forename: R A
authors.initials: RA
authors.lastname: Deyo
mesh_terms: D000328:Adult; D000368:Aged; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000145:classification / Q000473:pathology; D017116:Low Back Pain / Q000145:classification* / Q000473:pathology*; D008159:Lumbar Vertebrae / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015588:Observer Variation