Fat-free mass depletion in patients with COPD in Brazil: development of a new cutoff point and its relation with mortality and extrapulmonary manifestations.

Abstract

None of the cutoff points for fat-free mass index (FFMI) were tested for the Brazilian population, and it is unknown whether the available ones are able to discriminate extrapulmonary disease manifestations. This cross-sectional study aims to develop and validate a cutoff point for FFM depletion based on Brazilian patients with chronic obstructive pulmonary disease (COPD) and to verify its association and of previously published cutoffs with extrapulmonary manifestations. A new cutoff point was obtained from the best FFMI value for discrimination of preserved exercise capacity in a sample of patients (n=57). The discriminative capacity was assessed in another sample (n=96). The new cutoff point and other previously published ones were tested to discriminate low exercise capacity, physical inactivity, sedentary lifestyle and low quality of life. A receiver operation characteristics curve with area under the curve (AUC) value was plotted and each cutoff points' discriminative capacity was calculated. Cox regression and Kaplan-Meier method assessed the association between the cutoff points and mortality. The new cutoff points for FFMI were 14.65 kg/m2 for women (AUC=0.744; sensitivity (Se)=0.88; specificity (Sp)=0.60) and 20.35 kg/m2 for men (AUC=0.565; Se=0.36; Sp=0.81). The new cutoffs were the best to discriminate poor exercise capacity assessed by walked distance in % predicted and quality of life. Only the new cutoff point was associated with mortality (HR=2.123; 95% CI: 1.03-4.33, P=0.039, log rank P=0.035). Only the new cutoff point was associated with all-cause mortality, and it had the highest discriminating capacity for exercise capacity and quality of life in Brazilian patients with COPD.