POSTN and asthma: In addition to these markers, however, periostin is becoming increasingly relevant in clinical practice, this despite the findings of Korevaar et al., who showed that in severe asthma, there is a poor correlation between the number of eosinophils in blood, FeNO, periostin, and serum IgE levels on the one hand and the number of eosinophils in sputum (14).