Liquid chromatography/mass spectrometry analysis of exhaled leukotriene B4 in asthmatic children

Abstract Background The role of leukotriene (LT) B 4 , a potent inflammatory mediator, in atopic asthmatic and atopic nonasthmatic children is largely unknown. The lack of a gold standard technique for measuring LTB 4 in exhaled breath condensate (EBC) has hampered its quantitative assessment in this biological fluid. We sought to measure LTB 4 in EBC in atopic asthmatic children and atopic nonasthmatic children. Exhaled nitric oxide (NO) was measured as an independent marker of airway inflammation. Methods Fifteen healthy children, 20 atopic nonasthmatic children, 25 steroid-naïve atopic asthmatic children, and 22 atopic asthmatic children receiving inhaled corticosteroids were studied. The study design was of cross-sectional type. Exhaled LTB 4 concentrations were measured using liquid chromatography/mass spectrometry-mass spectrometry (LC/MS/MS) with a triple quadrupole mass spectrometer. Exhaled NO was measured by chemiluminescence with a single breath on-line method. LTB 4 values were expressed as the total amount (in pg) of eicosanoid expired in the 15-minute breath test. Kruskal-Wallis test was used to compare groups. Results Compared with healthy children [87.5 (82.5–102.5) pg, median and interquartile range], exhaled LTB 4 was increased in steroid-naïve atopic asthmatic [255.1 (175.0–314.7) pg, p < 0.001], but not in atopic nonasthmatic children [96.5 (87.3–102.5) pg, p = 0.59)]. Asthmatic children who were receiving inhaled corticosteroids had lower concentrations of exhaled LTB 4 than steroid-naïve asthmatics [125.0 (25.0–245.0) pg vs 255.1 (175.0–314.7) pg, p < 0.01, respectively]. Exhaled NO was higher in atopic nonasthmatic children [16.2 (13.5–22.4) ppb, p < 0.05] and, to a greater extent, in atopic steroid-naïve asthmatic children [37.0 (31.7–57.6) ppb, p < 0.001] than in healthy children [8.3 (6.1–9.9) ppb]. Compared with steroid-naïve asthmatic children, exhaled NO levels were reduced in asthmatic children who were receiving inhaled corticosteroids [15.9 (11.5–31.7) ppb, p < 0.01]. Conclusion In contrast to exhaled NO concentrations, exhaled LTB 4 values are selectively elevated in steroid-naïve atopic asthmatic children, but not in atopic nonasthmatic children. Although placebo control studies are warranted, inhaled corticosteroids seem to reduce exhaled LTB 4 in asthmatic children. LC/MS/MS analysis of exhaled LTB 4 might provide a non-invasive, sensitive, and quantitative method for airway inflammation assessment in asthmatic children.