Reliability of the Brazilian Portuguese version of the fatigue severity scale and its correlation with pulmonary function, dyspnea, and functional capacity in patients with COPD*

OBJECTIVE To describe the intra-rater and inter-rater reliability of the Brazilian Portuguese version of the fatigue severity scale (FSS) in patients with COPD and to identify the presence of its association with parameters of pulmonary function, dyspnea, and functional capacity. METHODS This was an observational cross-sectional study involving 50 patients with COPD, who completed the FSS in interviews with two researchers in two visits. The FSS scores were correlated with those of the Medical Research Council (MRC) scale, as well as with FEV1, FVC, and six-minute walk distance (6MWD). RESULTS The mean age of the patients was 69.4 ± 8.23 years, whereas the mean FEV1 was 46.5 ± 20.4% of the predicted value. The scale was reliable, with an intraclass correlation coefficient of 0.90 (95% CI, 0.81-0.94; p < 0.01). The FSS scores showed significant correlations with those of MRC scale (r = 0.70; p < 0.01), as well as with 6MWD (r = -0.77; p < 0.01), FEV1 (r = -0.38; p < 0.01), FVC (r = -0.35; p < 0.01), and stage of the disease in accordance with the Global Initiative for Chronic Obstructive Lung Disease criteria (r = 0.37; p < 0.01). CONCLUSIONS The Brazilian Portuguese version of the FSS proved reliable for use in COPD patients in Brazil and showed significant correlations with sensation of dyspnea, functional capacity, pulmonary function, and stage of the disease.