Agreement of different reference equations to classify patients with COPD as having reduced or preserved 6MWD.

BACKGROUND: Interpretation of the six-minute walk distance (6MWD) is enhanced by using recommended reference equations. Whenever possible, the choice of equation should be region-specific. A potential problem is that different equations for the 6MWD may have been developed for the same population, and it may be complicated to choose the most suitable. OBJECTIVE: To verify the agreement of different reference equations in classifying patients with Chronic Obstructive Pulmonary Disease (COPD) as having reduced or preserved 6MWD. METHODS: 159 patients with COPD performed the six-minute walk test according to international standardization. They were classified as having reduced 6MWD if it was below the lower limit of normal. Five Brazilian equations (Iwama; Britto1; Britto2; Dourado; Soares) and the two non-Brazilian equations most cited worldwide (Troosters; Enright) were used. The agreement for patients classified as reduced or preserved 6MWD was verified by Cohen's Kappa (pair-to-pair) analysis. The proportion of patients classified as having reduced walked distance was compared by the Chi-squared test. RESULTS: Agreement between equations varied largely in classifying subjects as having reduced or preserved 6MWD (Kappa: 0.10-0.82). Brazilian equations with the highest agreement were Iwama, Britto1 and Britto2 (Kappa>0.75). The proportion of patients classified as having reduced 6MWD was statistically similar only between equations in which the agreement was higher than 0.70. CONCLUSION: Even reference equations from the same country vary considerably in the classification of reduced or preserved 6MWD, and it is recommended that the region-specific ones be used as they give with higher agreement for similar and comparable interpretation of the patients' functional exercise capacity.

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

BACKGROUND/OBJECTIVES: 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.

Mucociliary clearance and its relation with the level of physical activity in daily life in healthy smokers and nonsmokers.

OBJECTIVES: To investigate the relationship between mucociliary transport and physical activity in daily life (PADL) in smokers and nonsmokers. METHODS: Fifty-two current smokers were submitted to assessment of mucociliary transport (Sacharin Transit Time, STT), carbon monoxide levels in the exhaled air, lung function and smoking history. In addition, subjects kept a pedometer worn at the waist for six days in order to determine their level of PADL (steps/day). The tests were also performed on 30 matched healthy nonsmokers who served as control group. RESULTS: Light smokers (≤15 cigarettes/day) had a STT of 9 (7-11) min (median [confidence interval]), which was similar to nonsmokers (8 [8-11]min; p=0.8). Both moderate (16-25 cigarettes/day) and heavy (>25 cigarettes/day) smokers had significantly higher STT (13 [11-17] min and 13 [10-21] min, respectively) than nonsmokers and light smokers (p<0.05 for all). There was no difference in the number of steps/day between any of the groups (p>0.05 for all). In the general group of smokers, STT was not significantly correlated with PADL, pack/years index, years of smoking or age (r<-0.23; p>0.09 for all). There was significant negative correlation between STT and PADL only in light smokers (r=-0.55; p=0.02) and nonsmokers (r=-0.42; p=0.02), but not in moderate and heavy smokers. CONCLUSION: In light smokers and non-smokers, better mucociliary function is associated to higher daily physical activity level, as opposed to the decreased mucociliary function observed in smokers, i.e., those with moderate and heavy cigarette consumption.