Published Online: May 2016
Asthma is not one disease, but many. Moreover, each asthma subtype, or phenotype, has defined characteristics which relate to key disease features, underlying allergic sensitization, overall severity, pulmonary physiology, and responsiveness to treatment. Guideline-directed care is evidence-based and has provided guidance to greater treatment effectiveness by graded therapeutic levels and assessment of disease control. However, because asthma has many faces, or phenotypes, it is not surprising that a “one-sized approach” does not achieve disease control for all patients. Consequently, efforts to a more precise or individualized approach are necessary to be more effective in asthma care.
How to get to precision medicine in asthma requires greater insight to markers of asthma that regulate disease in individual patients and to then use this information to more effectively select treatment based upon underlying disease features or mechanisms.
Berry and Busse discuss one step in this progress: the emergence of biomarkers in asthma and how their application will be an important next step to more effectively and precisely treat asthma. Their perspective focuses on four biomarkers in asthma: eosinophils, exhaled nitric oxide (FeNO), periostin, and IgE. Each of these biomarkers relates to an aspect of asthma, i.e. presence of disease or etiology, and with the emergence of biological treatments, these markers will take on greater importance for patient selection and treatment choice.
Eosinophils in the lung are an inflammatory component in most asthma patients, often relate to disease severity, and vary depending upon course of disease or treatment. Eosinophils are under control of products from subpopulations of lymphocytes, such as interleukin-5 released from Th2 cells and innate lymphoid cells. For most patients, inhaled corticosteroids (ICS) lead to disease control and, linked to decreased sputum eosinophils. However, for some patients, eosinophils persist despite appropriate treatment and even high doses of ICS or systemic corticosteroids. In this setting, risks for exacerbations increase and usual treatments do not prevent these events. The monoclonal antibodies, mepolizumab and reslizumab, reduce eosinophils, an event associated with clinical improvement and the prevention of exacerbations. Therefore, the persistence of blood eosinophils serves as a very telling biomarker of these patients’ risk and likely benefit from treatment directed against the eosinophils.
As Berry and Busse conclude, progress to identify biomarkers in asthma are ongoing and of importance. The need for more biomarkers, and especially those with greater specificity and predictability is essential to achieve greater treatment precision and improved disease control.
The Journal of Allergy and Clinical Immunology (JACI) is the official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.