Is oxidative stress associated with disease severity, pulmonary function and metabolic syndrome in chronic obstructive pulmonary disease? / ¿Está el estrés oxidativo asociado a la gravedad de la enfermedad, a la función pulmonar y al síndrome metabólico en la enfermedad pulmonar obstructiva crónica?

OBJECTIVE: To investigate associations between oxidant/antioxidant biomarkers with the disease severity, pulmonary function and diagnosis of metabolic syndrome (MetS) in patients with COPD. METHODS: Seventy-four subjects were included, 39 with COPD (age 69±7 years; female 41%) and 35 for control group (age 69±7 years; female 43%). They were diagnosed with MetS and allocated in one of 4 subgroups: COPD and control, with and without MetS, respectively. Advanced oxidation protein products (AOPP), paraoxonase-1, catalase activity, sulfhydryl group and total lipid hydroperoxide were assayed. Pulmonary function was performed with a plethysmograph. RESULTS: COPD severity (GOLD≥3) and pulmonary function were associated with sulfhydryl group and AOPP (P≤.03 for all). The prevalence of MetS was associated with AOPP in COPD (P=.04). Individuals with COPD and MetS showed higher AOPP compared to COPD without MetS (P<.0001). CONCLUSION: COPD severity, worse pulmonary function and presence of metabolic syndrome are associated with oxidative stress in individuals with COPD.

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.