Serum potential biomarkers according to sputum inflammatory cell profiles in adult asthmatics

Background/Aims: Asthma is not a single disease but, rather, a heterogeneous inflammatory disorder with various pathogenic mechanisms. We analyzed the associations between the cellular profile of sputum and the serum levels of inflammatory mediators/cytokines in a cohort of adult asthmatics. Methods: We recruited 421 adult asthmatic patients. All subjects were classified into four groups according to their sputum cellular profiles: G1, eosinophilic; G2, mixed granulocytic; G3, neutrophilic; and G4, paucigranulocytic. Serum levels of cytokines and mediators including periostin, eosinophil-derived neurotoxin (EDN), S100A9, and folliculin were quantified. Results: Among 421 patients, G1 accounted for 149 (35.4%), G2 for 71 (16.9%), G3 for 155 (36.8%), and G4 for 46 (10.9%). Serum periostin and EDN levels were significantly higher in G1 (p = 0.004, and p = 0.031) than in the others. Serum S100A9 levels were elevated in G2 and G3 (p = 0.008). Serum folliculin levels differed significantly among the four groups, with the highest level in G4 (p = 0.042). To identify G1 from G1 plus G2 groups, the optimal serum cut-off levels were 1.71 ng/mL for periostin, and 1.61 ng/mL for EDN. When these two parameters were combined, the sensitivity was 76.0% and the specificity was 64.3% (area under the curve, 0.701; p = 0.004). Conclusions: The serum periostin and EDN levels may be used as predictors to discriminate the eosinophilic asthma group from patients having eosinophilic or mixed granulocytic asthma, and the serum folliculin level is significantly elevated in patients with paucigranulocytic asthma compared to those with different inflammatory cell profile.