POSTN and chronic rhinosinusitis with nasal polyps: Serum levels of 8 cytokines and periostin were measured from the sera obtained from the adult patients with five different severe asthma phenotypes based on the presence/absence of aeroallergen sensitivity, peripheral eosinophilia and chronic rhinosinusitis with nasal polyposis (CRSwNP) during stable and exacerbation periods, and from the matched controls.