title: Construct Validation of a Multidimensional Computerized Adaptive Test for Fatigue in Rheumatoid Arthritis.
abstract: OBJECTIVE
  Multidimensional computerized adaptive testing enables precise measurements of patient-reported outcomes at an individual level across different dimensions. This study examined the construct validity of a multidimensional computerized adaptive test (CAT) for fatigue in rheumatoid arthritis (RA).
  
  
  METHODS
  The 'CAT Fatigue RA' was constructed based on a previously calibrated item bank. It contains 196 items and three dimensions: 'severity', 'impact' and 'variability' of fatigue. The CAT was administered to 166 patients with RA. They also completed a traditional, multidimensional fatigue questionnaire (BRAF-MDQ) and the SF-36 in order to examine the CAT's construct validity. A priori criterion for construct validity was that 75% of the correlations between the CAT dimensions and the subscales of the other questionnaires were as expected. Furthermore, comprehensive use of the item bank, measurement precision and score distribution were investigated.
  
  
  RESULTS
  The a priori criterion for construct validity was supported for two of the three CAT dimensions (severity and impact but not for variability). For severity and impact, 87% of the correlations with the subscales of the well-established questionnaires were as expected but for variability, 53% of the hypothesised relations were found. Eighty-nine percent of the items were selected between one and 137 times for CAT administrations. Measurement precision was excellent for the severity and impact dimensions, with more than 90% of the CAT administrations reaching a standard error below 0.32. The variability dimension showed good measurement precision with 90% of the CAT administrations reaching a standard error below 0.44. No floor- or ceiling-effects were found for the three dimensions.
  
  
  CONCLUSIONS
  The CAT Fatigue RA showed good construct validity and excellent measurement precision on the dimensions severity and impact. The dimension variability had less ideal measurement characteristics, pointing to the need to recalibrate the CAT item bank with a two-dimensional model, solely consisting of severity and impact.
authors.affiliation: Department of Psychology, Health & Technology, Faculty of Behavioral, Management and Social Sciences, University of Twente, Enschede, The Netherlands.|Expert Center for Chronic Fatigue, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Nikolaus
authors.affiliation: Department of Psychology, Health & Technology, Faculty of Behavioral, Management and Social Sciences, University of Twente, Enschede, The Netherlands.
authors.forename: Christina
authors.initials: C
authors.lastname: Bode
authors.affiliation: Department of Psychology, Health & Technology, Faculty of Behavioral, Management and Social Sciences, University of Twente, Enschede, The Netherlands.
authors.forename: Erik
authors.initials: E
authors.lastname: Taal
authors.affiliation: Department of Psychology, Health & Technology, Faculty of Behavioral, Management and Social Sciences, University of Twente, Enschede, The Netherlands.|Department of Rheumatology and Clinical Immunology, Medical Spectrum Twente, Enschede, The Netherlands.
authors.forename: Harald E
authors.initials: HE
authors.lastname: Vonkeman
authors.affiliation: Department of Research Methodology, Measurement and Data Analysis, Faculty of Behavioral, Management and Social Sciences, University of Twente, Enschede, The Netherlands.
authors.forename: Cees A W
authors.initials: CA
authors.lastname: Glas
authors.affiliation: Department of Psychology, Health & Technology, Faculty of Behavioral, Management and Social Sciences, University of Twente, Enschede, The Netherlands.|Department of Rheumatology and Clinical Immunology, Medical Spectrum Twente, Enschede, The Netherlands.
authors.forename: Mart A F J
authors.initials: MA
authors.lastname: van de Laar
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000473:pathology*; D003201:Computers; D005221:Fatigue / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011594:Psychometrics / Q000379:methods*; D015203:Reproducibility of Results; D057566:Self Report; D011795:Surveys and Questionnaires; D055815:Young Adult