title: Minimally important difference of Health Assessment Questionnaire in psoriatic arthritis: relating thresholds of improvement in functional ability to patient-rated importance and satisfaction.
abstract: OBJECTIVE
  To evaluate changes in function as measured by Health Assessment Questionnaire Disability Index (HAQ-DI) and the meaningfulness of the changes, in importance and satisfaction, in patients with psoriatic arthritis (PsA).
  
  
  METHODS
  HAQ-DI was assessed at baseline and at Weeks 4, 12, and 24 in a randomized double-blind study of 205 patients with active PsA receiving etanercept 25 mg twice weekly or placebo. Concurrently, patients rated the importance of and satisfaction with their change in function on a 7-point scale (1 = not at all important/satisfied; 7 = extremely important/satisfied). Mean HAQ-DI improvement corresponding to ratings of minimally (2-3) or very (6-7) important or satisfied was determined using a posthoc linear mixed-model analysis. Patient importance ratings were used as an anchor to estimate minimally important difference (MID) for HAQ-DI; distribution-based estimates were also calculated.
  
  
  RESULTS
  A total of 161 patients (69 placebo; 92 etanercept) had ≥ 1 HAQ-DI scores showing improvement from baseline and a corresponding importance or satisfaction rating. HAQ-DI improvements corresponding to importance scale ratings of 2 or 3 were 0.335 (95% CI 0.214, 0.455) and 0.360 (95% CI 0.263, 0.456), respectively, suggesting an MID of about 0.35. HAQ-DI improvements corresponding to satisfaction scale ratings of 2 and 3 were 0.293 (95% CI 0.230, 0.357) and 0.360 (95% CI 0.307, 0.413). For a given change in HAQ-DI, nearly two-thirds of patients indicated a lower rating for satisfaction than for importance. This trial was registered in the ClinicalTrials.gov registry (NCT00317499).
  
  
  CONCLUSIONS
  Our study suggests the MID for HAQ-DI in PsA is about 0.35. The results may also provide insight into patient satisfaction with changes in function and expectations for therapy.
authors: Swedish Medical Center and University of Washington, Seattle, WA 98104, USA. pmease@nwlink.com
authors: Philip J
authors: PJ
authors: Mease
authors: J Michael
authors: JM
authors: Woolley
authors: Bojena
authors: B
authors: Bitman
authors: Brian C
authors: BC
authors: Wang
authors: Denise R
authors: DR
authors: Globe
authors: Amitabh
authors: A
authors: Singh
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D018501:Antirheumatic Agents / Q000627:therapeutic use*; D015535:Arthritis, Psoriatic / Q000188:drug therapy* / Q000503:physiopathology; D004185:Disability Evaluation; D004311:Double-Blind Method; D000068800:Etanercept; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000627:therapeutic use*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D017060:Patient Satisfaction; D011788:Quality of Life; D018124:Receptors, Tumor Necrosis Factor / Q000627:therapeutic use*; D012649:Self Concept; D011795:Surveys and Questionnaires; D016896:Treatment Outcome
chemical_list: D018501:Antirheumatic Agents; D007074:Immunoglobulin G; D018124:Receptors, Tumor Necrosis Factor; D000068800:Etanercept