Reliability and utility of the 6-minute walk test in granulomatous-lymphocytic interstitial lung disease (GLILD)

<bold>Introduction:</bold> This study aimed to evaluate the reliability and validity of the Six-Minute Walk Test (6MWT) as an outcome measure in patients diagnosed with granulomatous-lymphocytic interstitial lung disease (GLILD), occurring in common variable immunodeficiency patients. <bold>Methods:</bold> Thirteen patients from the Respiratory Immunology Clinic at the Royal Free Hospital participated. Demographics and clinical data were recorded. The 6MWT was conducted at baseline and two follow-ups. Reliability was assessed using Intraclass Correlation Coefficient (ICC). Validity was evaluated by correlating 6MWT distance with clinical parameters. <bold>Results:</bold> Thirteen patients (54% male, mean age 47 ± 19 years) were included. Median 6MWT distance was 457 meters, with 3 walking <400m at baseline. No correlations found between 6MWT distance and age (p=0.07), gender (p=0.84), or systemic treatment (p=0.83). Excellent reliability was demonstrated (ICC=0.94, p<0.002). Standard Error of Measurement (SEM) and Minimal Detectable Change at 95% confidence (MDC95%) were 25m and 68m, respectively. Strong correlations were found between 6MWT distance and KBILD total score (r=0.665), and SF-36 physical functioning domain (r=0.577). Negative correlations were observed between MRC score for breathlessness and 6MWT distance (r=-0.827). No correlation found between baseline 6MWT distance and lung functions. <bold>Conclusion:</bold> The 6MWT demonstrates excellent reliability and validity in GLILD patients. Its correlations with clinical parameters suggest utility in assessing disease severity and treatment response.