title: Validity and measurement precision of the PROMIS physical function item bank and a content validity-driven 20-item short form in rheumatoid arthritis compared with traditional measures.
abstract: OBJECTIVE
  To evaluate the content validity and measurement properties of the Patient-Reported Outcome Measurement Information System (PROMIS) physical function item bank and a 20-item short form in patients with RA in comparison with the HAQ disability index (HAQ-DI) and 36-item Short Form Health Survey (SF-36) physical functioning scale (PF-10).
  
  
  METHODS
  The content validity of the instruments was evaluated by linking their items to the International Classification of Functioning, Disability and Health (ICF) core set for RA. The measures were administered to 690 RA patients enrolled in the Dutch Rheumatoid Arthritis Monitoring registry. Measurement precision was evaluated using item response theory methods and construct validity was evaluated by correlating physical function scores with other clinical and patient-reported outcome measures.
  
  
  RESULTS
  All 207 health concepts identified in the physical function measures referred to activities that are featured in the ICF. Twenty-three of 26 ICF RA core set domains are featured in the full PROMIS physical function item bank compared with 13 and 8 for the HAQ-DI and PF-10, respectively. As hypothesized, all three physical function instruments were highly intercorrelated (r 0.74-0.84), moderately correlated with disease activity measures (r 0.44-0.63) and weakly correlated with age (rs 0.07-0.14). Item response theory-based analysis revealed that a 20-item PROMIS physical function short form covered a wider range of physical function levels than the HAQ-DI or PF-10.
  
  
  CONCLUSIONS
  The PROMIS physical function item bank demonstrated excellent measurement properties in RA. A content-driven 20-item short form may be a useful tool for assessing physical function in RA.
authors.affiliation: Arthritis Center Twente, Department of Psychology, Health & Technology, Enschede, a.h.oudevoshaar@utwente.nl.
authors.forename: Martijn A H
authors.initials: MA
authors.lastname: Oude Voshaar
authors.affiliation: Arthritis Center Twente, Department of Psychology, Health & Technology, Enschede.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Ten Klooster
authors.affiliation: Department of Research Methodology, Measurement and Data Analysis, University of Twente.
authors.forename: Cees A W
authors.initials: CA
authors.lastname: Glas
authors.affiliation: Arthritis Center Twente, Department of Psychology, Health & Technology, Enschede, Arthritis Center Twente, Department of Rheumatology and Clinical Immunology, Medisch Spectrum Twente, Enschede, The Netherlands.
authors.forename: Harald E
authors.initials: HE
authors.lastname: Vonkeman
authors.affiliation: Arthritis Center Twente, Department of Psychology, Health & Technology, Enschede.
authors.forename: Erik
authors.initials: E
authors.lastname: Taal
authors.affiliation: Stanford ARAMIS Program, Stanford University School of Medicine, Palo Alto, CA, USA.
authors.forename: Eswar
authors.initials: E
authors.lastname: Krishnan
authors.affiliation: Department of Rheumatology, Ziekenhuisgroep Twente.
authors.forename: Hein J
authors.initials: HJ
authors.lastname: Bernelot Moens
authors.affiliation: Department of Epidemiology and Biostatistics, VU University Medical Center, Amsterdam and.
authors.forename: Maarten
authors.initials: M
authors.lastname: Boers
authors.affiliation: Department of Epidemiology and Biostatistics, VU University Medical Center, Amsterdam and.
authors.forename: Caroline B
authors.initials: CB
authors.lastname: Terwee
authors.affiliation: Department of Rheumatic Diseases, Radboud University Medical Centre, Nijmegen, The Netherlands.
authors.forename: Piet L C M
authors.initials: PL
authors.lastname: van Riel
authors.affiliation: Arthritis Center Twente, Department of Psychology, Health & Technology, Enschede, Arthritis Center Twente, Department of Rheumatology and Clinical Immunology, Medisch Spectrum Twente, Enschede, The Netherlands.
authors.forename: Mart A F J
authors.initials: MA
authors.lastname: van de Laar
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000503:physiopathology* / Q000534:rehabilitation; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D063868:Patient Outcome Assessment; D015203:Reproducibility of Results; D012720:Severity of Illness Index
keywords: HAQ; PROMIS; item bank; physical function