title: Influence of the experience of the reader on reliability of joint space width measurement. A cross-sectional multiple reading study in hip osteoarthritis.
abstract: OBJECTIVE
  The objectives were to evaluate improvement in reliability of joint space width (JSW) measurements, according to the previous experience of the readers in hip osteoarthritis (OA).
  
  
  METHODS
  Fifty radiographs in hip OA patients from a randomized controlled trial (ECHODIAH) were read 12 times by two readers with different levels of experience in radiographic interpretation. Intra-reader reliability and inter-reader reliability were assessed through calculation of the smallest detectable difference (SDD) and the intra-class correlation coefficient (ICC).
  
  
  RESULTS
  Intra-reader reliability: for the experienced reader, no significant change in SDD was observed with repeated JSW measurements. For the junior reader, the SDD decreased significantly from 0.90 mm to 0.65 mm (P=0.002). A plateau of SDD was reached after reading 200 to 300 radiographs, with a value close to the mean SDD of the experienced reader (0.67 mm). ICCs were high (>0.88) for both the senior and the junior readers. Inter-reader reliability: no improvement in inter-reader reliability was noted with repeated measurements of JSW (SDD=0.81 mm). However, no additional training sessions were performed. ICCs were high (>0.85).
  
  
  CONCLUSIONS
  This study indicated for the first time a learning curve in analyzing JSW in hip OA for an inexperienced reader. After analyzing 200 to 300 radiographs, the junior reader reached an intra-reader reliability similar to the experienced reader. Moreover, the information brought by the ICC was not sufficient, suggesting that the SDD should be systematically reported in studies evaluating OA radiographic progression, on top of the ICC, to help in interpreting the JSW reliability.
authors.affiliation: Department of Rheumatology, Dijon University Hospital, Medicine Faculty, Burgundy University, 3, rue du Faubourg-Raines, 21000 Dijon, France. paul.ornetti@chu-dijon.fr
authors.forename: Paul
authors.initials: P
authors.lastname: Ornetti
authors.forename: Jean-Francis
authors.initials: JF
authors.lastname: Maillefert
authors.forename: Simon
authors.initials: S
authors.lastname: Paternotte
authors.forename: Maxime
authors.initials: M
authors.lastname: Dougados
authors.forename: Laure
authors.initials: L
authors.lastname: Gossec
mesh_terms: D000368:Aged; D001175:Arthrography / Q000592:standards* / Q000706:statistics & numerical data*; D003430:Cross-Sectional Studies; D016208:Databases, Factual / Q000706:statistics & numerical data*; D004056:Differential Threshold; D018450:Disease Progression; D006621:Hip Joint / Q000000981:diagnostic imaging*; D006801:Humans; D008875:Middle Aged; D015337:Multicenter Studies as Topic; D015588:Observer Variation; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging*; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results