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Responsiveness and minimally important difference for the Patient-Reported Outcomes Measurement Information System (PROMIS) 20-item physical functioning short form in a prospective observational study of rheumatoid arthritis
  1. Ron D Hays1,2,
  2. Karen L Spritzer1,
  3. James F Fries3,
  4. Eswar Krishnan3
  1. 1Department of Medicine, UCLA Division of General Internal Medicine & Health Services Research, Los Angeles, California, USA
  2. 2RAND, Santa Monica, California, USA
  3. 3Stanford ARAMIS Program, Stanford University School of Medicine, Palo Alto, California, USA
  1. Correspondence to Professor Ron D Hays, UCLA Department of Medicine, Division of General Internal Medicine & Health Services Research, 911 Broxton Avenue, Los Angeles, CA 90095-1736, USA; drhays{at}ucla.edu

Abstract

Objective To estimate responsiveness (sensitivity to change) and minimally important difference (MID) for the Patient-Reported Outcomes Measurement Information System (PROMIS) 20-item physical functioning scale (PROMIS PF-20).

Methods The PROMIS PF-20, short form 36 (SF-36) physical functioning scale, and Health Assessment Questionnaire (HAQ) were administered at baseline, and 6 and 12 months later to a sample of 451 persons with rheumatoid arthritis. A retrospective change (anchor) item was administered at the 12-month follow-up. We estimated responsiveness between 12 months and baseline, and between 12 months and 6 months using one-way analysis of variance F-statistics. We estimated the MID for the PROMIS PF-20 using prospective change for people reporting getting ‘a little better’ or ‘a little worse’ on the anchor item.

Results F-statistics for prospective change on the PROMIS PF-20, SF-36 and HAQ by the anchor item over 12 and 6 months (in parentheses) were 16.64 (14.98), 12.20 (7.92) and 10.36 (12.90), respectively. The MID for the PROMIS PF-20 was 2 points (about 0.20 of an SD).

Conclusions The PROMIS PF-20 is more responsive than two widely used (‘legacy’) measures. The MID is a small effect size. The measure can be useful for assessing physical functioning in clinical trials and observational studies.

  • Outcomes Research
  • Health Services Research
  • Rheumatoid Arthritis

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