ABSTRACT
Asthma is a heterogeneous disease, in which asthmatic patients present with different clinical phenotypes, variable endotypes, and different response to asthma medicines. Thus, we are faced with an asthma paradox; asthma is diagnosed subjectively by clinical history and treated with biologically active drugs. To solve this paradox, we need objective airway biomarkers to tailor the proper medications to the proper patient. Biomarkers should have one or more of the following characteristics: 1] could differentiate poor symptoms perceivers from over-perceivers, 2] could predict disease activity and hence disease outcome, 3] could clarify asthma phenotype responders from non-responders, and finally 4] could characterize different clinical asthma phenotypes. Therefore, we have conducted a review of literature trying to apply those four parameters to different airway inflammatory biomarkers. We found that FeNO fulfilled the four proposed clinical parameters of airway inflammatory biomarkers whereas; serum periostin was the single best systemic biomarker of airway luminal and tissue eosinophilia in severe uncontrolled TH2 asthma phenotype. Thus, this may be considered a trial towards tailoring the proper medication to the proper patient. However, application of biomarkers in clinical practice requires easier and cheaper techniques together with standardized methods for sample collection and analysis