title: The Pfirrmann classification of lumbar intervertebral disc degeneration: an independent inter- and intra-observer agreement assessment.
abstract: Grading inter-vertebral disc degeneration (IDD) is important in the evaluation of many degenerative conditions, including patients with low back pain. Magnetic resonance imaging (MRI) is considered the best imaging instrument to evaluate IDD. The Pfirrmann classification is commonly used to grade IDD; the authors describing this classification showed an adequate agreement using it; however, there has been a paucity of independent agreement studies using this grading system. The aim of this study was to perform an independent inter- and intra-observer agreement study using the Pfirrmann classification.
  
  
  
  T2-weighted sagittal images of 79 patients consecutively studied with lumbar spine MRI were classified using the Pfirrmann grading system by six evaluators (three spine surgeons and three radiologists). After a 6-week interval, the 79 cases were presented to the same evaluators in a random sequence for repeat evaluation. The intra-class correlation coefficient (ICC) and the weighted kappa (wκ) were used to determine the inter- and intra-observer agreement.
  
  
  
  The inter-observer agreement was excellent, with an ICC = 0.94 (0.93-0.95) and wκ = 0.83 (0.74-0.91). There were no differences between spine surgeons and radiologists. Likewise, there were no differences in agreement evaluating the different lumbar discs. Most differences among observers were only of one grade. Intra-observer agreement was also excellent with ICC = 0.86 (0.83-0.89) and wκ = 0.89 (0.85-0.93).
  
  
  
  In this independent study, the Pfirrmann classification demonstrated an adequate agreement among different observers and by the same observer on separate occasions. Furthermore, it allows communication between radiologists and spine surgeons.
authors.affiliation: Department of Orthopaedic Surgery, School of Medicine, Pontificia Universidad Catolica de Chile, Marcoleta 352, Santiago, Chile. jurrutia@med.puc.cl.
authors.forename: Julio
authors.initials: J
authors.lastname: Urrutia
authors.affiliation: Department of Orthopaedic Surgery, School of Medicine, Pontificia Universidad Catolica de Chile, Marcoleta 352, Santiago, Chile.
authors.forename: Pablo
authors.initials: P
authors.lastname: Besa
authors.affiliation: Department of Orthopaedic Surgery, School of Medicine, Pontificia Universidad Catolica de Chile, Marcoleta 352, Santiago, Chile.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Campos
authors.affiliation: Department of Radiology, School of Medicine, Pontificia Universidad Catolica de Chile, Santiago, Chile.
authors.forename: Pablo
authors.initials: P
authors.lastname: Cikutovic
authors.affiliation: Department of Radiology, School of Medicine, Pontificia Universidad Catolica de Chile, Santiago, Chile.
authors.forename: Mario
authors.initials: M
authors.lastname: Cabezon
authors.affiliation: Department of Orthopaedic Surgery, School of Medicine, Pontificia Universidad Catolica de Chile, Marcoleta 352, Santiago, Chile.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Molina
authors.affiliation: Department of Radiology, School of Medicine, Pontificia Universidad Catolica de Chile, Santiago, Chile.
authors.forename: Juan Pablo
authors.initials: JP
authors.lastname: Cruz
mesh_terms: D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000473:pathology; D055959:Intervertebral Disc Degeneration / Q000145:classification / Q000000981:diagnostic imaging / Q000473:pathology; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results
keywords: Agreement study; Disc degeneration; Disc degeneration classification; Lumbar spine; Magnetic resonance imaging