Utility of the 6-minute walk test and health-related quality of life questionnaires in granulomatous and lymphocytic interstitial lung disease

INTRODUCTION: Granulomatous lymphocytic interstitial lung disease (GLILD) is a non-infectious complication affecting 10-20% of patients with common variable immunodeficiency disorders. Exercise capacity in GLILD patients, who often report shortness of breath during exercise, has not been previously evaluated. This study aimed to assess the utility of the six-minute walk test (6MWT) as an outcome measure in GLILD. It also evaluated reproducibility and effectiveness of King's Brief ILD Questionnaire (K-BILD) questionnaire in capturing the multidimensional impact of GLILD on quality of life. METHODS: This was an observational prospective cohort study. The 6MWT and questionnaires were conducted at baseline and two follow-ups. The 6MWT was performed according to ERS/ATS guidelines. The utility was evaluated by correlating the 6MWT measures (walked distance (6MWD) and distance-saturation product (DSP)) with clinical parameters and health-related quality of life (HRQOL) questionnaires. Reproducibility was assessed using the Intraclass Correlation Coefficient. RESULTS: Thirteen participants (54% male, median age 45 (IQR 38- 62) years) were included. The median 6MWT distance was 457 meters. DSP was the only measure strongly correlated with FVC% and FEV1%, and it showed stronger correlations with clinical measures than 6MWD. The 6MWT has good 6-month and one year reproducibility. Finally, K-BILD appeared to be a useful tool for assessing HRQOL in patients with GLILD, who often have multi-system involvement. CONCLUSION: Our findings highlight the potential of the 6MWT as a useful measure to assess GLILD. The 6MWT and K-BILD correlations with clinical parameters suggest utility in assessing disease severity and monitoring patients' physical functioning.