title: The relationship between quantitative measures of disc height and disc signal intensity with Pfirrmann score of disc degeneration.
abstract: OBJECTIVE
  To assess the relationship between quantitative measures of disc height and signal intensity with the Pfirrmann disc degeneration scoring system and to test the inter-rater reliability of the quantitative measures.
  
  
  METHODS
  Participants were 76 people who had recently recovered from their last episode of acute low back pain and underwent MRI scan on a single 3T machine. At all 380 lumbar discs, quantitative measures of disc height and signal intensity were made by 2 independent raters and compared to Pfirrmann scores from a single radiologist. For quantitative measures of disc height and signal intensity a "raw" score and 2 adjusted ratios were calculated and the relationship with Pfirrmann scores was assessed. The inter-tester reliability of quantitative measures was also investigated.
  
  
  RESULTS
  There was a strong linear relationship between quantitative disc signal intensity and Pfirrmann scores for grades 1-4, but not for grades 4 and 5. For disc height only, Pfirrmann grade 5 had significantly reduced disc height compared to all other grades. Results were similar regardless of whether raw or adjusted scores were used. Inter-rater reliability for the quantitative measures was excellent (ICC > 0.97).
  
  
  CONCLUSIONS
  Quantitative measures of disc signal intensity were strongly related to Pfirrmann scores from grade 1 to 4; however disc height only differentiated between grade 4 and 5 Pfirrmann scores. Using adjusted ratios for quantitative measures of disc height or signal intensity did not significantly alter the relationship with Pfirrmann scores.
authors.affiliation: Physical Therapy Department,Tehran university of Medical Sciences, District 12, Enghelab, Pich-e-Shemiran, Tehran, Iran.
authors.forename: Sara
authors.initials: S
authors.lastname: Salamat
authors.affiliation: Faculty of Medicine and Health Sciences, Macquarie University, Talavera Rd North Ryde, Sydney, NSW 2109 Australia.
authors.forename: John
authors.initials: J
authors.lastname: Hutchings
authors.affiliation: Faculty of Medicine and Health Sciences, Macquarie University, Talavera Rd North Ryde, Sydney, NSW 2109 Australia.
authors.forename: Clemens
authors.initials: C
authors.lastname: Kwong
authors.affiliation: Macquarie Medical Imaging, Macquarie University Hospital, Talavera Rd North Ryde, Sydney, NSW 2109 Australia.
authors.forename: John
authors.initials: J
authors.lastname: Magnussen
authors.affiliation: Faculty of Medicine and Health Sciences, Macquarie University, Talavera Rd North Ryde, Sydney, NSW 2109 Australia.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Hancock
keywords: Correlation; Diagnosis; Disc degeneration; Disc height; Disc signal; Imaging; Low back pain; Magnetic resonance imaging; Pfirrmann scores; Reliability; Validity