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.SUBJECTS/METHODS:
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.RESULTS:
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).CONCLUSIONS:
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.