Comparison of Airway and Systemic Malondialdehyde Levels for Assessment of Oxidative Stress in Cystic Fibrosis.

INTRODUCTION: Oxidative stress plays a pivotal role in the pathogenesis of cystic fibrosis (CF). In this study, airway and systemic oxidative stress was investigated in CF using malondialdehyde (MDA), an established by-product of polyunsaturated fatty acid peroxidation.
METHODS: Exhaled breath condensate (EBC), sputum, and plasma were collected from 40 stable CF patients during routine clinical visits and from 25 healthy controls. MDA was measured by high-performance liquid chromatography.
RESULTS: MDA levels in sputum (279.8 ± 14.7 vs. 92.7 ± 9.2 nmol/L, p < 0.0001), EBC (139.9 ± 6.7 vs. 71.5 ± 4.3 nmol/L, p < 0.0001), and plasma (176.1 ± 15.9 vs. 129.6 ± 12.9 nmol/L, p < 0.05) were increased in patients with CF compared to healthy controls. MDA measurement in sputum [area under receiver operating characteristic curve (AUC): 0.977, p < 0.0001] or EBC (AUC: 0.94, p < 0.0001) discriminated between patients and controls with greater accuracy than in plasma (AUC: 0.677, p < 0.05). Sputum and EBC MDA levels were elevated in patients with severe pulmonary dysfunction [forced expiratory volume in 1 s (FEV1) <50 % predicted] compared to those with mild-to-moderate functional impairment (FEV1 ≥50 % predicted) (p < 0.05). MDA concentrations in CF patients colonized either with Pseudomonas aeruginosa or with other bacteria were similar (p = NS). The intra- and inter-assay repeatabilities of MDA measurements was similar in all the three types of samples, while the between-visit variability was higher in plasma.
CONCLUSIONS: MDA is a potential new airway marker of oxidative stress in patients with CF. Sputum MDA differentiates best between patients and healthy subjects.