Serum periostin but not airway POSTN expression is reduced in smokers with asthma

Background Elevated serum periostin is associated with airway eosinophilia in non-smokers with asthma and may predict response to therapies targeting Th 2 inflammation. Smoking in asthma is associated with non-eosinophilic airway inflammation and corticosteroid insensitivity. We determined the effects of smoking status on serum periostin and airway expression in asthma. Methods Serum periostin (ELISA; Aviscera Bioscience) and airway (nasal) epithelial POSTN expression (210809_s_at on U133+2 chips) were measured in asthmatic and healthy subjects (Table). Serum periostin was also measured before and after two week oral steroids in another asthma group (n=45). Data (median IQR) was analysed by Kruskal-Wallis test. Results Serum periostin was reduced by smoking in both asthmatic (p=0.017) and healthy subjects (p=0.063). Periostin was not influenced by disease severity (p=0.786). Oral steroid treatment reduced serum periostin (p=0.030), particularly in non-smokers with asthma. POSTN expression was similar in non-smokers and smokers with severe asthma, but lower in healthy smokers (p=0.002). Conclusion Serum periostin is lowered by smoking in asthma, whereas airway POSTN expression is similar in smokers and non-smokers with asthma. The role of periostin as a potential biomarker of Th 2 inflammation in asthma requires further evaluation in smokers.