title: Scoring haemophilic arthropathy on X-rays: improving inter- and intra-observer reliability and agreement using a consensus atlas.
abstract: OBJECTIVE
  The radiological Pettersson score (PS) is widely applied for classification of arthropathy to evaluate costly haemophilia treatment. This study aims to assess and improve inter- and intra-observer reliability and agreement of the PS.
  
  
  METHODS
  Two series of X-rays (bilateral elbows, knees, and ankles) of 10 haemophilia patients (120 joints) with haemophilic arthropathy were scored by three observers according to the PS (maximum score 13/joint). Subsequently, (dis-)agreement in scoring was discussed until consensus. Example images were collected in an atlas. Thereafter, second series of 120 joints were scored using the atlas. One observer rescored the second series after three months. Reliability was assessed by intraclass correlation coefficients (ICC), agreement by limits of agreement (LoA).
  
  
  RESULTS
  Median Pettersson score at joint level (PSjoint) of affected joints was 6 (interquartile range 3-9). Using the consensus atlas, inter-observer reliability of the PSjoint improved significantly from 0.94 (95 % confidence interval (CI) 0.91-0.96) to 0.97 (CI 0.96-0.98). LoA improved from ±1.7 to ±1.1 for the PSjoint. Therefore, true differences in arthropathy were differences in the PSjoint of >2 points. Intra-observer reliability of the PSjoint was 0.98 (CI 0.97-0.98), intra-observer LoA were ±0.9 points.
  
  
  CONCLUSIONS
  Reliability and agreement of the PS improved by using a consensus atlas.
  
  
  CONCLUSIONS
  • Reliability of the Pettersson score significantly improved using the consensus atlas. • The presented consensus atlas improved the agreement among observers. • The consensus atlas could be recommended to obtain a reproducible Pettersson score.
authors.affiliation: Department of Radiology, University Medical Center Utrecht, HP E01.132, Post Office Box 85500, 3508 GA, Utrecht, The Netherlands. w.foppen@umcutrecht.nl.
authors.forename: Wouter
authors.initials: W
authors.lastname: Foppen
authors.affiliation: Department of Radiology, University Medical Center Utrecht, HP E01.132, Post Office Box 85500, 3508 GA, Utrecht, The Netherlands.
authors.forename: Irene C
authors.initials: IC
authors.lastname: van der Schaaf
authors.affiliation: Department of Radiology, University Medical Center Utrecht, HP E01.132, Post Office Box 85500, 3508 GA, Utrecht, The Netherlands.
authors.forename: Frederik J A
authors.initials: FJ
authors.lastname: Beek
authors.affiliation: Department of Radiology, University Medical Center Utrecht, HP E01.132, Post Office Box 85500, 3508 GA, Utrecht, The Netherlands.|Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Helena M
authors.initials: HM
authors.lastname: Verkooijen
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands.|Van Creveldkliniek, Department of Hematology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Kathelijn
authors.initials: K
authors.lastname: Fischer
mesh_terms: D000328:Adult; D000843:Ankle Joint / Q000000981:diagnostic imaging*; D032921:Consensus; D005260:Female; D006467:Hemophilia A / Q000150:complications*; D006801:Humans; D007592:Joint Diseases / Q000175:diagnosis* / Q000209:etiology; D007596:Joints / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D011859:Radiography / Q000379:methods*; D015203:Reproducibility of Results; D012720:Severity of Illness Index
keywords: Agreement; Arthropathy; Haemophilia; Reliability; X-rays