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

• Published in: Annals of the rheumatic diseases Vol. 74; no. 1; pp. 104 - 107
• Main Authors: Hays, Ron D, Spritzer, Karen L, Fries, James F, Krishnan, Eswar
• Format: Journal Article
• Language: English
• Published: England 01.01.2015
• Subjects: Activities of Daily Living; Aged; Arthritis, Rheumatoid - physiopathology; Arthritis, Rheumatoid - therapy; Female; Humans; Male; Middle Aged; Patient Outcome Assessment; Prospective Studies; Reproducibility of Results; Self Report; Surveys and Questionnaires; Rheumatoid Arthritis; Health Services Research; Outcomes Research
• ISSN: 0003-4967; 1468-2060
• DOI: 10.1136/annrheumdis-2013-204053

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). 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. 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). 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.