Six Minute Walk Test: A Tool for Predicting Mortality in Chronic Pulmonary Diseases

INTRODUCTION: Six Minute Walk Test (6MWT) is a simple test used to measure exercise capacity in Chronic Pulmonary Diseases (CPDs). Decreased exercise capacity significantly affects the quality of life. The 6MWT is a known tool to measure exercise capacity and quality of life in CPD. However, the role of change in follow up Six Minute Walk Distance (6MWD) in assessing mortality and its correlation with known prognostic factors haven't been tested to the best of our knowledge. AIM: To study the correlation of change in 6MWD with change in spirometry and to study the role of 6MWD in predicting mortality in CPD. SETTINGS AND DESIGN: Prospective cohort study. MATERIALS AND METHODS: A total of 139 CPD patients were grouped into obstructive, restrictive and post Tuberculosis (TB) sequelae. Optimized treatment was given and they were followed up regularly. Spirometry and 6MWT was done at the beginning and after one year. Mean decline in FEV1, FVC was correlated with mean decline in 6MWD. STATISTICAL ANALYSIS: With STATA 13.1 correlation between 6MWT and spirometric values were done using Wilcoxon signed rank test. Predictors of mortality were studied using multivariate analysis. RESULTS: Overall mean decline in 6MWD was 16.07 m/year. There was no correlation between mean change in 6MWD and change in FEV1, FVC, and FEV1/FVC. On multivariate analysis, 6MWD was the better predictor of mortality than FEV1 (p<0.001), FVC (p<0.001). At cut off value of 240 meters, sensitivity and specificity of 6MWT in predicting mortality was 71.05% and 81.94% respectively. CONCLUSION: The 6MWD changes independently and has no correlation with change in spirometry, it is an independent predictor of mortality in CPD.