Higher blood eosinophil levels after omalizumab treatment may be associated with poorer asthma outcomes

Eosinophilic asthma is characterized by high eosinophil levels in induced sputum and peripheral blood. Elevated airway eosinophil counts can be detected in more than 50% of asthmatics and associated with more symptoms, frequent exacerbations, and greater airflow limitation.1 Increased blood eosinophils (BEs) also predict a greater response to new biological therapies (mepolizumab, reslizumab).2 Higher pretreatment BE levels are also related to a better response to omalizumab,3 which reduces BE, fractional exhaled nitric oxide (FENO), serum periostin, and exacerbations.4,5 Therefore, a higher effect on eosinophil count reduction may lead to greater clinical improvements. Accordingly, if omalizumab response is eosinophilic dependent, it might be reduced in subjects with persistent high BE counts after antiIgE therapy.