Responsiveness and minimal clinically important difference of SGRQ-I and K-BILD in idiopathic pulmonary fibrosis

Thomas Skovhus Prior,Ole Hilberg,Saher Burhan Shaker,Nils Hoyer,Jesper Rømhild Davidsen,Elisabeth Bendstrup

doi:10.1186/s12931-020-01359-3

Abstract

BackgroundIdiopathic pulmonary fibrosis (IPF) specific version of St. George’s Respiratory Questionnaire (SGRQ-I) and King’s Brief Interstitial Lung Disease questionnaire (K-BILD) are validated health-related quality of life (HRQL) instruments, but no or limited data exist on their responsiveness and minimal clinically important difference (MCID). The objectives of this study were to assess responsiveness of SGRQ-I and K-BILD and determine MCID separately for deterioration and improvement in a large, prospective cohort of patients with IPF in a real-world setting.MethodsConsecutive patients with IPF were recruited. SGRQ-I, K-BILD, SGRQ, Shortness of Breath Questionnaire, pulmonary function tests and 6-min walk test measurements were obtained at baseline and at six and 12 months; at six and 12 months, patients also completed Global Rating of Change Scales. Responsiveness was assessed using correlation coefficients and linear regression. Cox regression was used for mortality analyses. MCID was estimated using receiver operating characteristic curves with separate analyses for improvement and deterioration.ResultsA total of 150 IPF patients were included and 124 completed the 12-month follow-up. Based on all HRQL anchors and most physiological anchors, responsiveness analyses supported the evidence pointing towards SGRQ-I and K-BILD as responsive instruments. Multivariate analyses showed an association between SGRQ-I and mortality (HR: 1.18, 95% CI: 1.02 to 1.36, p = 0.03) and a trend was found for K-BILD (HR: 0.82, 95% CI: 0.64 to 1.05, p = 0.12). MCID was estimated for all domains of SGRQ-I and K-BILD. MCID for improvement differed from deterioration for both SGRQ-I Total (3.9 and 4.9) and K-BILD Total (4.7 and 2.7).ConclusionsSGRQ-I and K-BILD were responsive to change concerning both HRQL and most physiological anchors. MCID was determined separately for improvement and deterioration, resulting in different estimates; especially a smaller estimate for deterioration compared to improvement in K-BILD.Trial registrationClinicaltrials.gov, no. NCT02818712. Registered 30 June 2016.

Highlights

Idiopathic pulmonary fibrosis (IPF) specific version of St
Δ: Change from baseline to 12 months; St. George’s Respiratory Questionnaire (SGRQ-I) IPF-specific version of the Saint George’s Respiratory Questionnaire, K-BILD King’s Brief Interstitial Lung Disease questionnaire, CI Confidence interval, Global Rating of Change Scales (GRCS) Global rating of change scales, SOBQ University of California San Diego Shortness of Breath questionnaire, SGRQ Saint George’s Respiratory Questionnaire, forced vital capacity (FVC)% Forced vital capacity % predicted, DLCO% Diffusing capacity of the lung for carbon monoxide % predicted, 6MWD Distance walked during the 6-min walk test trend was found for K-BILD (HR: 0.82, 95% CI: 0.64 to 1.05, p = 0.12)
Δ: Change from baseline to 12 months; SGRQ-I: IPF-specific version of the Saint George’s Respiratory Questionnaire, K-BILD: King’s Brief Interstitial Lung Disease questionnaire, CI: Confidence interval, GRCS: Global Rating of Change Scales, SOBQ: University of California San Diego Shortness of Breath questionnaire, SGRQ: Saint George’s Respiratory Questionnaire, FVC: Forced vital capacity, DLCO: Diffusing capacity of the lung for carbon monoxide, 6MWD: Distance walked during the 6-min walk test

Summary

Introduction

Idiopathic pulmonary fibrosis (IPF) specific version of St. George’s Respiratory Questionnaire (SGRQ-I) and King’s Brief Interstitial Lung Disease questionnaire (K-BILD) are validated health-related quality of life (HRQL) instruments, but no or limited data exist on their responsiveness and minimal clinically important difference (MCID). The objectives of this study were to assess responsiveness of SGRQ-I and K-BILD and determine MCID separately for deterioration and improvement in a large, prospective cohort of patients with IPF in a real-world setting. Idiopathic pulmonary fibrosis (IPF) is the most burdensome interstitial lung disease (ILD). It is a chronic, fibrotic lung disease characterised by progressive decline in lung function and increasing dyspnoea [1]. Along with a wide range of comorbidities, patients with IPF often experience impaired health-related quality of life (HRQL) [2, 3]. Antifibrotic treatments successfully slow down lung function decline, but do not improve HRQL convincingly [5, 6]

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