title: Establishing a Common Metric for Physical Function: Linking the HAQ-DI and SF-36 PF Subscale to PROMIS(®) Physical Function.
abstract: BACKGROUND
  Physical function (PF) is a common health concept measured in clinical trials and clinical care. It is measured with different instruments that are not directly comparable, making comparative effectiveness research (CER) challenging when PF is the outcome of interest.
  
  
  OBJECTIVE
  Our goal was to establish a common reporting metric, so that scores on commonly used physical function measures can be converted into PROMIS scores.
  
  
  METHODS
  Following a single-sample linking design, all participants completed items from the NIH Patient Reported Outcomes Measurement Information System (PROMIS®) Physical Function (PROMIS PF) item bank and at least one other commonly used "legacy" measure: the Health Assessment Questionnaire (HAQ) or the Short Form-36 physical function ten-item PF scale (SF-36 PF). A common metric was created using analyses based on item response theory (IRT), producing score cross-walk tables.
  
  
  METHODS
  Participants (N = 733) were part of an internet panel, many of whom reported one or more chronic health conditions.
  
  
  METHODS
  PROMIS PF, SF-36 PF, and the HAQ-Disability Index (HAQ-DI).
  
  
  RESULTS
  Our results supported the hypothesis that all three scales measure essentially the same concept. Cross-walk tables for use in CER are therefore justified.
  
  
  CONCLUSIONS
  HAQ-DI and SF-36 PF results can be expressed on the PROMIS PF metric for the purposes of CER and other efforts to compare PF results across studies that utilize any one of these three measures. Clinicians seeking to incorporate PROs into their clinics can collect patient data on any one of these three instruments and estimate the equivalent on the other two.
authors.affiliation: Department of Medical Social Sciences, Northwestern University Feinberg School of Medicine, 625 N. Michigan Avenue, Suite 2700, Chicago, IL, 60611, USA. b-schalet@northwestern.edu.
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Schalet
authors.affiliation: Outcomes Research, Evidera, Bethesda, MD, USA.
authors.forename: Dennis A
authors.initials: DA
authors.lastname: Revicki
authors.affiliation: Department of Medical Social Sciences, Northwestern University Feinberg School of Medicine, 625 N. Michigan Avenue, Suite 2700, Chicago, IL, 60611, USA.
authors.forename: Karon F
authors.initials: KF
authors.lastname: Cook
authors.affiliation: Department of Medicine, Stanford University School of Medicine, Palo Alto, CA, USA.
authors.forename: Eswar
authors.initials: E
authors.lastname: Krishnan
authors.affiliation: Department of Medicine, Stanford University School of Medicine, Palo Alto, CA, USA.
authors.forename: Jim F
authors.initials: JF
authors.lastname: Fries
authors.affiliation: Department of Medical Social Sciences, Northwestern University Feinberg School of Medicine, 625 N. Michigan Avenue, Suite 2700, Chicago, IL, 60611, USA.
authors.forename: David
authors.initials: D
authors.lastname: Cella
mesh_terms: D000203:Activities of Daily Living; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006306:Health Surveys / Q000379:methods / Q000592:standards*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010809:Physical Fitness / Q000502:physiology*; D057566:Self Report / Q000592:standards*; D011795:Surveys and Questionnaires / Q000592:standards; D055815:Young Adult
keywords: HAQ-DI; PRO; PROMIS; SF-36; patient-reported outcome; physical function; score linking