Methods: The study was conducted in 104 Japanese adult patients with bronchial asthma (BA). EBC and induced sputum were collected at the same time and analyzed for 15 kinds of cytokines, chemokines, and chemical mediators using ELISA assays.
Results: In the EBC, the proportion of data below the limit of detection (LOD) was 27% for histamine and more than 80% for 14 other variables. Particularly, all data were below LOD for TIMP-1, TGF-β1, IL-4, eotaxin, IFN-γ, and IL-13. In the induced sputum, the proportion of data below LOD was more than 80% for IL-4 and IFN-γ, 60 to 80% for FGF, TIMP-1, PDGF AA, TGF-β1, eotaxin, and MMP-9, 20 to 40% for TNF-α, IL-12, and IL-13, 14% for IL-5, and 4% for VEGF. The proportion of data below LOD was significantly higher in the EBC than in the induced sputum (p<0.05 – 0.001). Furthermore, observed values were generally higher in the induce sputum than in the EBC (p<0.05 – 0.001). In the analysis using FeNO and sputum eosinophil percentage as airway inflammation markers, VEGF in induced sputum was most highly correlated with inflammation in BA (p<0.05).
Conclusions: Cytokines, chemokines, and chemical mediators can be determined with higher accuracy in induced sputum than in EBC. Particularly, VEGF in induced sputum is important as a marker of airway inflammation.