It is hoped that the development of reliable biomarkers that reflect underlying pathobiological processes in asthma, potentially including blood eosinophils, FeNO, IgE, periostin, dipeptidyl peptidase 4 and allergen specific IgE testing would help to accurately identify patient phenotypes, in an effort to best tailor therapy to improve asthma outcomes. The gene discussed is DPP4; the disease is asthma.