title: Patient-Reported Outcomes Measurement Information System (PROMIS) instruments among individuals with symptomatic knee osteoarthritis: a cross-sectional study of floor/ceiling effects and construct validity.
abstract: BACKGROUND
  The psychometric properties of Patient Reported Outcomes Measurement Information System (PROMIS) instruments have been explored in a number of general and clinical samples. No study, however, has evaluated the psychometric function of these measures in individuals with symptomatic knee osteoarthritis (KOA). The aim of this project was to evaluate the construct (structural) validity and floor/ceiling effects of four PROMIS measures in this population.
  
  
  METHODS
  We conducted a secondary analysis of baseline data from a randomized trial comparing Tai Chi and physical therapy. Participants completed four PROMIS static short-form instruments (i.e., Anxiety, Depression, Physical Function, and Pain Interference) as well as six well-validated (legacy) measures that assess pain, function, and psychological health. We calculated descriptive statistics and percentages of participants scoring the minimum (floor) and maximum (ceiling) possible scores for PROMIS and legacy measures. We also estimated the association between PROMIS scores and scores on legacy measures using Spearman's rank correlations coefficients.
  
  
  RESULTS
  Data from 204 participants were analyzed. Mean age of the sample was 60 years; 70% were female. The PROMIS Anxiety and Depression had floor effects with 17 and 24% of participants scoring the minimum, respectively. PROMIS Anxiety and Depression scores had strongest associations with general mental health, including stress (Perceived Stress Scale, r ≥ 0.65) and depression (Beck Depression Index-II, r = 0.70). PROMIS Pain Interference scores correlated most strongly with measures of whole body pain (Short-Form 36 Bodily Pain, r = -0.73) and physical health (Short-Form 36 Physical-Component Summary, r = -0.73); their correlations were lower with other legacy measures, including with the WOMAC knee-specific pain (r = 0.47). PROMIS Physical Function scores had stronger associations with scores on the Short-Form 36 Physical Function (r = 0.79) than with scores on other legacy measures.
  
  
  CONCLUSIONS
  The four PROMIS static-short forms performed well among individuals with symptomatic knee osteoarthritis as evidenced in correlations with legacy measures. PROMIS Anxiety and Depression target general mental health (e.g., stress, depression), and PROMIS Pain Interference and Physical Function static-short forms target whole-body outcomes among participants with symptomatic knee osteoarthritis. Floor effects in the PROMIS Anxiety and Depression scores should be considered if needing to distinguish among patients with very low levels of these outcomes.
  
  
  BACKGROUND
  Clinicaltrials.gov NCT01258985. Registered 10 December 2010.
authors.affiliation: Division of Rheumatology, Tufts Medical Center, 800 Washington Street, Box #406, Boston, MA, 02111, USA. jeffrey.driban@tufts.edu.
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Driban
authors.affiliation: Division of Rheumatology, Tufts Medical Center, 800 Washington Street, Box #406, Boston, MA, 02111, USA. nlmorgan@hawaii.edu.|Internal Medicine Residency Program, John A Burns School of Medicine, University of Hawaii, Honolulu, HI, USA. nlmorgan@hawaii.edu.
authors.forename: Nani
authors.initials: N
authors.lastname: Morgan
authors.affiliation: The Institute for Clinical Research and Health Policy Studies, Tufts Medical Center, and Tufts Clinical and Translational Science Institute, Tufts University, 800 Washington Street, Box #63, Boston, MA, 02111, USA. LPrice1@tuftsmedicalcenter.org.
authors.forename: Lori Lyn
authors.initials: LL
authors.lastname: Price
authors.affiliation: Department of Medical Social Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA. karon.cook@northwestern.edu.
authors.forename: Karon F
authors.initials: KF
authors.lastname: Cook
authors.affiliation: Division of Rheumatology, Tufts Medical Center, 800 Washington Street, Box #406, Boston, MA, 02111, USA. CWang2@tuftsmedicalcenter.org.
authors.forename: Chenchen
authors.initials: C
authors.lastname: Wang
mesh_terms: D000368:Aged; D001007:Anxiety / Q000175:diagnosis / Q000453:epidemiology / Q000628:therapy; D003430:Cross-Sectional Studies; D003863:Depression / Q000175:diagnosis / Q000453:epidemiology / Q000628:therapy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000175:diagnosis* / Q000453:epidemiology / Q000628:therapy; D010147:Pain Measurement / Q000592:standards*; D063868:Patient Outcome Assessment; D026741:Physical Therapy Modalities; D015203:Reproducibility of Results; D057566:Self Report / Q000592:standards*; D026302:Tai Ji