title: Interobserver and intraobserver variability in interpretation of lumbar disc abnormalities. A comparison of two nomenclatures.
abstract: METHODS
  A double-blind prospective study was used to measure interobserver and intraobserver variability when interpreting lumbar spine magnetic resonance imaging studies of disc abnormalities.
  
  
  OBJECTIVE
  To evaluate reader consistency when interpreting disc extension beyond the interspace, and assess the effect of two distinct nomenclatures on reader consistency.
  
  
  BACKGROUND
  Interobserver and intraobserver variability in interpretation of lumbar disc abnormalities is an important consideration in analyzing the technical efficacy of an imaging modality. However, this has not been well measured (particularly for standardized nomenclature).
  
  
  METHODS
  Magnetic resonance imaging studies of the lumbar spine performed prospectively in 98 asymptomatic volunteers, and an additional 27 selected studies from symptomatic patients, were read blindly by two experienced neuroradiologists, using two separate nomenclatures. Only the discs were evaluated (625 interspaces). Nomenclature I was normal, bulge, herniation. Nomenclature II was normal, bulge, protrusion, extrusion. Intraobserver and interobserver variation were measured with Kappa statistic analysis.
  
  
  RESULTS
  Interobserver agreement was 80% for both nomenclatures with a Kappa statistic of 0.58. Intraobserver agreement was 86% for each reader, with a Kappa statistic of 0.71 and 0.69, respectively. The most common disagreement was for normal versus bulge. The next most common disagreement (5-6%) was for bulge versus herniation (or protrusion in Nomenclature II). Herniation was read in 23% of the asymptomatic subjects. Using Nomenclature II, protrusion was seen in 27% of these subjects. Extrusion was read in only two asymptomatic subjects.
  
  
  CONCLUSIONS
  Experienced readers using standardized nomenclature showed moderate to substantial agreement with interpreting disc extension beyond the interspace on magnetic resonance imaging.
authors.affiliation: Hoag Memorial Hospital, Newport Beach, California, USA.
authors.forename: M N
authors.initials: MN
authors.lastname: Brant-Zawadzki
authors.forename: M C
authors.initials: MC
authors.lastname: Jensen
authors.forename: N
authors.initials: N
authors.lastname: Obuchowski
authors.forename: J S
authors.initials: JS
authors.lastname: Ross
authors.forename: M T
authors.initials: MT
authors.lastname: Modic
mesh_terms: D000328:Adult; D004311:Double-Blind Method; D006801:Humans; D007403:Intervertebral Disc / Q000473:pathology*; D007405:Intervertebral Disc Displacement / Q000175:diagnosis*; D008159:Lumbar Vertebrae / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011446:Prospective Studies; D012189:Retrospective Studies; D009626:Terminology as Topic