Minimum important difference of the EQ-5D-5L and EQ-VAS in fibrotic interstitial lung disease.

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). 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. 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. 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.

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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.