SOD3 and chronic obstructive pulmonary disease: EcSOD activity in COPD patients at different GOLD stages (I/II/III/IV: 110.13 ± 18.45/110.79 ± 19.77/109.42 ± 20.69/116.18 ± 16.20 U/ml, respectively, p = 0.145) or smoking status (current smoker/former smoker/never smoker: 113.81 ± 19.31/109.66 ± 20.15/112.09 ± 18.13 U/ml, respectively, p = 0.237) during exacerbations were not significantly different.