Responsiveness and minimal clinically important difference of K-BILD and SGRQ-I

Abstract

Introduction: Limited data exist on the responsiveness and minimal clinically important difference (MCID) of King’s Brief Interstitial Lung Disease questionnaire (K-BILD) and the idiopathic pulmonary fibrosis (IPF)-specific version of St. George’s Respiratory Questionnaire (SGRQ-I). This study aimed to assess responsiveness of K-BILD and SGRQ-I and to determine the MCID in a real-world, multicentre cohort of IPF patients. Methods: SGRQ-I, K-BILD and other questionnaires, pulmonary function tests and 6-minute walk test were completed at baseline and at six and 12 months. Responsiveness was assessed by correlation coefficients and MCID was estimated by ROC curves for improvement and deterioration separately. Results: A total of 150 IPF patients were included; 124 completed the study (82.7%). K-BILD and SGRQ-I scores responded to changes over 12 months in the majority of anchors. MCID estimates were 2.7-4.7 for K-BILD total and 3.9-4.9 for SGRQ-I total score (see table). Conclusions: K-BILD and SGRQ-I have good longitudinal validity in IPF patients. MCID estimates differed for improvement and deterioration. These differences should be considered, when evaluating changes in health-related quality of life.