Estimating minimally important differences for the PROMIS pain interference scales: Results from 3 randomized clinical trials

Chen X. Chen, Kurt Kroenke, Timothy E. Stump, Jacob Kean, Janet S. Carpenter, Erin E. Krebs, Matthew J. Bair, Teresa M. Damush, Patrick O. Monahan

Research output: Contribution to journalArticlepeer-review

139 Scopus citations

Abstract

Minimally important difference (MID) refers to the smallest meaningful difference that carries implications for patient care. Minimally important differences are necessary to help interpret patient-reported pain outcomes in research and clinical practice. The PROMIS pain interference scales were validated across diverse samples; however, more information about their MIDs could improve their interpretability. The purpose of this study was to estimate MIDs for 4 fixed-length PROMIS pain interference scales, including the 6-item Pain Short Form and the 4-, 6-, and 8-item pain interference scales used in the PROMIS profile instruments. Data were analyzed from 3 randomized controlled trials (N = 759). The 3 samples, respectively, consisted of patients with chronic low back pain (n = 261), chronic back pain or hip/knee osteoarthritis pain (n = 240), and a history of stroke (n = 258). For each sample, anchor- and distribution-based approaches were used to estimate MIDs. Standard error of measurement and effect sizes were used as distribution-based MID estimates. Anchor-based MID estimates were established by mapping PROMIS pain interference scores onto established anchor measures, including the Brief Pain Inventory, and retrospective and prospective global ratings of change. The distribution- and anchor-based MID estimates showed convergence. For the pain samples, MID estimates ranged from 2 to 3 T-score points. For the nonpain sample, MID estimates ranged from 3.5 to 4.5 T-score points. The MID estimates were comparable across the 4 fixed-length scales. These MIDs can be used to evaluate treatment effects in research and clinical care and to calculate estimates for powering clinical trials.

Original languageEnglish (US)
Pages (from-to)775-782
Number of pages8
JournalPain
Volume159
Issue number4
DOIs
StatePublished - Apr 1 2018

Bibliographical note

Publisher Copyright:
© 2017 International Association for the Study of Pain.

Keywords

  • Minimally important difference
  • PROMIS
  • Pain interference
  • Pain measurement
  • Patient-reported outcome measures
  • Psychometrics

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