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Original research
Minimum important difference of the EQ-5D-5L and EQ-VAS in fibrotic interstitial lung disease
  1. Amy Po Yu Tsai1,
  2. Seo Am Hur1,
  3. Alyson Wong1,2,
  4. Mohsen Safavi3,
  5. Deborah Assayag4,
  6. Kerri A Johannson5,
  7. Julie Morisset6,
  8. Charlene Fell5,
  9. Jolene H Fisher7,
  10. Hélène Manganas6,
  11. Shane Shapera7,
  12. Gerard Cox8,
  13. Andrea S Gershon7,9,10,
  14. Nathan Hambly8,
  15. Nasreen Khalil1,
  16. Teresa To10,11,
  17. Pearce George Wilcox1,
  18. Andrew Halayko12,
  19. Martin RJ Kolb8,
  20. Christopher J Ryerson1,2
  1. 1 The University of British Columbia Department of Medicine, Vancouver, British Columbia, Canada
  2. 2 Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, British Columbia, Canada
  3. 3 Respiratory Evaluation Sciences Program, Collaboration for Outcomes Research and Evaluation, Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, Canada
  4. 4 McGill University Department of Medicine, Montreal, Quebec, Canada
  5. 5 Department of Medicine, University of Calgary, Calgary, Alberta, Canada
  6. 6 Département de Médecine, Centre Hospitalier de l'Université de Montréal, Montreal, Quebec, Canada
  7. 7 University of Toronto Faculty of Medicine, Toronto, Ontario, Canada
  8. 8 Firestone Institute for Respiratory Health, McMaster University Department of Medicine, Hamilton, Ontario, Canada
  9. 9 Medicine, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada
  10. 10 Child Health Evaluative Sciences, The Hospital for Sick Children, Toronto, Ontario, Canada
  11. 11 University of Toronto Dalla Lana School of Public Health, Toronto, Ontario, Canada
  12. 12 Departments of Internal Medicine and Physiology and Pathophysiology, University of Manitoba, Winnipeg, Manitoba, Canada
  1. Correspondence to Dr Christopher J Ryerson, The University of British Columbia Department of Medicine, Vancouver, BC V1Y 1T3, Canada; chris.ryerson{at}


Rationale The European Quality of Life 5-Dimensions 5-Levels questionnaire (EQ-5D-5L) is a multidimensional patient-reported questionnaire that supports calculation of quality-adjusted life-years. Our objectives were to demonstrate feasibility of use and to calculate the minimum important difference (MID) of the EQ-5D-5L and its associated visual analogue scale (EQ-VAS) in patients with fibrotic interstitial lung disease (ILD).

Methods Patients who completed the EQ-5D-5L were identified from the prospective multicentre CAnadian REgistry for Pulmonary Fibrosis. Validity, internal consistency and responsiveness of the EQ-5D-5L were assessed, followed by calculation of the MID for the EQ-5D-5L and EQ-VAS. Anchor-based methods used an unadjusted linear regression against pulmonary function tests (PFTs) and dyspnoea and other quality of life questionnaires. Distribution-based method used one-half SD and SE measurement (SEM) calculations.

Results 1816 patients were analysed, including 472 (26%) with idiopathic pulmonary fibrosis. EQ-5D-5L scores were strongly correlated with the dyspnoea and other quality of life questionnaires and weakly associated with PFTs. The estimated MID for EQ-5D-5L ranged from 0.0050 to 0.054 and from 0.078 to 0.095 for the anchor-based and distribution-based methods, respectively. The MID for EQ-VAS ranged from 0.5 to 5.0 and from 8.0 to 9.7 for the anchor-based and distribution-based methods. Findings were similar across ILD subtypes, sex and age.

Conclusion We used a large and diverse cohort of patients with a variety of fibrotic ILD subtypes to suggest validity and MID of both the EQ-5D-5L and EQ-VAS. These findings will assist in designing future clinical trials and supporting cost-effectiveness analyses of potential treatments for patients with fibrotic ILD.

  • interstitial fibrosis
  • health economist

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  • Contributors Study conceptualisation and design: CJR and APYT. Data collection: all authors. Statistical analysis: APYT, SAH and CJR. Interpretation of results: all authors. Manuscript preparation: APYT, SAH, AWW and CJR. Approval of final version of the manuscript: all authors.

  • Funding CARE-PF is funded by Boehringer Ingelheim. Grant number 20R23666. The sponsor did not have input on any aspect of this work.

  • Competing interests CJR, MRJK, JM, KF, NH and DA report personal fees and grants from Boehringer Ingelheim and Hoffman La Roche outside the submitted work. HM reports grants from Boehringer Ingelheim. SS reports personal fees and grants from Boehringer Ingelheim and AstraZeneca Canada, and participation in clinical trials as site PI in Prometric Canada, Sanofi-Aventis, Gilead Pharmaceuticals, and Galapagos. KF also reports personal fees and grants from Theravance, Blade Therapeutics, Chest Foundation, University of Calgary School of Medicine, Pulmonary Fibrosis Society of Calgary, UCB Biopharma SPRL. NH also reports personal fees and grants from Actelion, Bayer and Novartis. MK also reports personal fees and grants from GSK, Gilead, Actelion, Respivert, Genoa, Alkermes, Pharmaxis, Prometric, Indalo and Third Pole. DA also reports personal fees and grants from Novartis. APYT, AW, SAH, GC, PGW, JF, MS, AG, CF, NK, AH and TT report no competing interests.

  • Patient consent for publication Not required.

  • Ethics approval The research ethics boards of all CARE-PF centres approved this substudy (coordinating centre: University of British Columbia and Providence Healthcare Research Ethics Board #H18-00993).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available upon reasonable request. Deidentified participant data are available upon request from the corresponding author. Research Ethics Board and CARE-PF Steering Committee approvals are required before release of any data.