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Minimally important difference in diffuse systemic sclerosis: results from the d-penicillamine study
  1. D Khanna1,
  2. D E Furst2,
  3. R D Hays3,5,
  4. G S Park2,4,
  5. W K Wong4,
  6. J R Seibold6,
  7. M D Mayes7,
  8. B White8,*,
  9. F F Wigley9,
  10. M Weisman10,
  11. W Barr11,
  12. L Moreland12,
  13. T A Medsger Jr13,
  14. V D Steen14,
  15. R W Martin15,
  16. D Collier16,
  17. A Weinstein14,
  18. E V Lally17,
  19. J Varga11,
  20. S R Weiner2,
  21. B Andrews18,
  22. M Abeles19,
  23. P J Clements2
  1. 1Division of Immunology, Department of Medicine; Institute for the Study of Health, University of Cincinnati, Cincinnati, Ohio, USA; Veterans Affairs Medical Center, Cincinnati
  2. 2Department of Medicine, Division of Rheumatology, David Geffen School of Medicine, Los Angeles, California, USA
  3. 3Division of General Internal Medicine and Health Services Research, David Geffen School of Medicine
  4. 4Department of Biostatistics, David Geffen School of Medicine
  5. 5RAND, Los Angeles
  6. 6University of Michigan Scleroderma Program, Ann Arbor, Michigan, USA
  7. 7Division of Rheumatology and Clinical Immunogenetics, The University of Texas—Houston Medical School, Houston, Texas, USA
  8. 8Department of Rheumatology and Clinical Immunology, University of Maryland School of Medicine, Baltimore, Maryland, USA
  9. 9Rheumatology Division, The Johns Hopkins University, Baltimore, Maryland, USA
  10. 10Division of Rheumatology, Cedars-Sinai Medical Center, Los Angeles
  11. 11Division of Rheumatology, Northwestern University Medical School, Chicago, Illinois, USA
  12. 12Divison of Clinical Immunology and Rheumatology, University of Alabama at Birmingham, Birmingham, Alabama, USA
  13. 13Division of Rheumatology and Clinical Immunology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
  14. 14Division of Rheumatology, Georgetown University Medical Center, Washington, DC, USA
  15. 15Division of Rheumatology, College of Human Medicine, Michigan State University, Grand Rapids, Michigan, USA
  16. 16Division of Rheumatology, University of Colorado Health Sciences Center, Denver, Colorado, USA
  17. 17Division of Rheumatology, Brown Medical School, Providence, Rhode Island, USA
  18. 18Division of Rheumatology, University of California, Irvine, California, USA
  19. 19Division of Rheumatic Diseases, University of Connecticut Health Center, Farmington, Connecticut, USA
  1. Correspondence to:
    D Khanna
    Division of Immunology, Department of Medicine, University of Cincinnati, ML 0563, Cincinnati, OH 45267-0563, USA;dinesh.khanna{at}uc.edu

Abstract

Objective: To estimate minimally important differences (MIDs) in scores for the modified Rodnan Skin Score (mRSS) and Health Assessment Questionnaire—Disability Index (HAQ-DI) in a clinical trial on diffuse systemic sclerosis (SSc).

Participants and methods: 134 people participated in a 2-year, double-blind, randomised clinical trial comparing efficacy of low-dose and high-dose d-penicillamine in diffuse SSc. At 6, 12, 18 and 24 months, the investigator was asked to rate the change in the patient’s health since entering the study: markedly worsened, moderately worsened, slightly worsened, unchanged, slightly improved, moderately improved or markedly improved. Patients who were rated as slightly improved were defined as the minimally changed subgroup and compared with patients rated as moderately or markedly improved.

Results: The MID estimates for the mRSS improvement ranged from 3.2 to 5.3 (0.40–0.66 effect size) and for the HAQ-DI from 0.10 to 0.14 (0.15–0.21 effect size). Patients who were rated to improve more than slightly were found to improve by 6.9–14.2 (0.86–1.77 effect size) on the mRSS and 0.21–0.55 (0.32–0.83 effect size) on the HAQ-DI score.

Conclusion: MID estimates are provided for improvement in the mRSS and HAQ-DI scores, which can help in interpreting clinical trials on patients with SSc and be used for sample size calculation for future clinical trials on diffuse SSc.

  • d-Pen, d-penicillamine
  • HAQ-DI, Health Assessment Questionnaire—Disability Index
  • HRQOL, health-related quality of life
  • MID, minimally important difference
  • mRSS, modified Rodnan Skin Score
  • SSc, systemic sclerosis

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Footnotes

  • * Current address: Amgen, Thousand Oaks, California, USA

  • Published Online First 15 March 2006

  • Funding: This study was supported in part by grants from the Scleroderma Federation; United Scleroderma Foundation; FDA Orphan Drug Program; Arthritis Foundation; CRC grant numbers M01RR00865 and M01RR00827; WH Conzen Endowment in Clinical Pharmacology of the Schering-Plough Foundation; and bequests from the estates of Winifred Krause, Morris Goldsmith and Takako Ito. DK was supported by the Arthritis and Scleroderma Foundations (Physician Scientist Development Award), the Scleroderma Foundation (New Investigator Award), a National Institutes of Health BIRCWH Award (grant number HD051953) and a grant from the Scleroderma Clinical Trial Consortium. RDH was supported in part by the UCLA/DREW Project EXPORT, National Institutes of Health, National Center on Minority Health & Health Disparities (P20-MD00148-01), the UCLA Center for Health Improvement in Minority Elders/Resource Centers for Minority Aging Research, National Institutes of Health, and National Institute of Aging (AG-02-004).

  • Competing interests: None declared.

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