The clinical applicability of oxidative stress markers detected in exhaled breath condensate and blood serum in evaluation of airway inflammation in asthma patients

Introduction:
There has been an increasing interest in using exhaled breath condensate (EBC) as a non-invasive method of detecting parameters of the airway, including oxidative stress biomarkers.

Aim:
Our aim was to estimate the oxidative stress in EBC in patients with moderate uncontrolled asthma (allergic and non-allergic) and to assess whether the intensity of that process may reflect the differentiation of asthma phenotypes.

Material and methods:
Forty-four patients (9 males, 35 females, age range: 35–59 years) with chronic moderate asthma were included in the study. The diagnosis was based on clinical history, physical findings and lung function tests. Thirty-one patients suffered from allergic asthma and 13 patients from non-allergic. In blood serum, erythrocyte hemolysate and in EBC the following oxidative stress parameters were estimated: superoxide dismutase (SOD), protein sulfhydryl groups (SH), catalase activity (CAT), glutathione reductase (GR), glutathione S-transferase (GST), glutathione peroxidase (GPx), malondialdehyde (MDA), total oxidation status (TOS), total antioxidant capacity (TAC), lipofuscin, ceruloplasmin, lipid peroxide concentration (LPH).

Results:
The oxidative stress markers were assessed both in peripheral blood and in EBC. In contrast to peripheral blood, only 4 markers (TAC, TOS, CAT and GST) were detectable in EBC. There were no significant differences in levels of those markers in EBC in patients with allergic and non-allergic asthma. Significantly higher oxidative stress parameter levels were detected in blood of non-allergic asthma patients with regards to CER (p = 0.008) and MDA (p = 0.014). Blood levels of LPS (p = 0.04) and SH (p = 0.014) were higher in allergic asthmatics.

Conclusions:
The inflammatory markers were elevated among non-allergic asthma patients. EBC is only partially useful to assess airway inflammation.