title: Items and dimensions for the construction of a multidimensional computerized adaptive test to measure fatigue in patients with rheumatoid arthritis.
abstract: OBJECTIVE
  Development of an item pool to construct a future computerized adaptive test (CAT) for fatigue in rheumatoid arthritis (RA). The item pool was based on the patients' perspective and examined for face and content validity previously. This study assessed the fit of the items with seven predefined dimensions and examined the item pool's dimensionality structure in statistical terms.
  
  
  METHODS
  A total of 551 patients with RA participated in this study. Several steps were conducted to come from an explorative item pool to a psychometrically sound item bank. The item response theory (IRT) analysis using the generalized partial credit model was conducted for each of the seven predefined dimensions. Poorly fitting items were removed. Finally, the best possible multidimensional IRT (MIRT) model for the data was identified.
  
  
  RESULTS
  In IRT analysis, 49 items showed insufficient item characteristics. Items with a discriminative ability below 0.60 and/or model misfit effect sizes greater than 0.10 were removed. Factor analysis on the 196 remaining items revealed three dimensions, namely severity, impact, and variability of fatigue. The dimensions were further confirmed in MIRT model analysis.
  
  
  CONCLUSIONS
  This study provided an initially calibrated item bank and showed which dimensions and items can be used for the development of a multidimensional CAT for fatigue in RA.
authors: Department of Psychology, Health & Technology, University of Twente, Faculty of Behavioral Sciences, P.O. Box 217, 7500 AE Enschede, The Netherlands. s.nikolaus@utwente.nl
authors: Stephanie
authors: S
authors: Nikolaus
authors: Christina
authors: C
authors: Bode
authors: Erik
authors: E
authors: Taal
authors: Johanna C M
authors: JC
authors: Oostveen
authors: Cees A W
authors: CA
authors: Glas
authors: Mart A F J
authors: MA
authors: van de Laar
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000503:physiopathology* / Q000523:psychology; D003936:Diagnosis, Computer-Assisted; D005221:Fatigue / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008960:Models, Psychological; D011594:Psychometrics; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D055815:Young Adult
keywords: Computerized adaptive test; Fatigue; Item response theory; Patient-reported outcome; Psychometrics; Rheumatoid arthritis