The 6-minute walk test as a prognostic marker in patients with silicosis

Introduction: The 6-minute walk test (6MWT) is a useful tool for pulmonary function evaluation in chronic respiratory diseases, but its value in silicosis is not well defined. Objective: The aim of this study is 1) to assess 6MWT in patients with silicosis and its relationship with pulmonary function test (PFT) and thoracic computed tomography (CT) findings; 2) to identify the clinical variables that reduce the 6MWT-distance. Method: Prospective observational study of patients with silicosis attended in our hospital from 2009 to 2017. PFT, thoracic CT and 6MWT (distance and O2 desaturation) were evaluated. Data were compared by different tests (Chi-square, Student-t, ANOVA, Pearson) as required. Results: 220 men with silicosis (77 simple, 143 complicated; mean age 52.3±10.5) were included. Mean 6MWT-distance was similar in both groups (simple 402±90m, complicated 387±92m; p=0.271). There were significant differences among complicated silicosis A: 407±97, B: 370±88, and C: 357±68 (p=0.022), respectively. The 6MWT correlated directly with PFT [FEV1 (r=0.47), FVC (r=0.37) and FEV1/FVC (r=0.54); p >0.001], and inversely with mMRC dyspnea scale (r=-0.60; p Conclusions: Reduced 6MWT-distance is found in complicated silicosis, and is associated with emphysema, more hospitalisations and higher mortality. These findings outlines the usefulness of 6MWT as a prognostic marker in silicosis.