Published Online: October 2016
The concept of asthma as a heterogeneous disease is supported by several observations, such as the variable clinical expression of the disease, including symptoms, pulmonary function bronchial hyperresponsiveness and treatment responses. The extent to which heterogeneity of treatment response and associated characteristics exist in inner-city children with asthma has not been defined.
In a study published in The Journal of Allergy & Clinical Immunology (JACI), Pongracic and colleagues report an investigation designed to determine distinct characteristics that differentiate difficult-to-control from easy-to-control asthma in inner-city children. Children aged 6-17 years with a broad range of asthma severity were enrolled. The subjects underwent baseline assessment followed by bi-monthly evaluation and management visits over an entire year during which standardized algorithms were used to optimize asthma management based upon National Asthma Education and Prevention Program Guidelines as well as to evaluate and manage rhinitis based upon Allergic Rhinitis and its Impact on Asthma Guidelines. Difficult-to-control and easy-to-control asthma were defined a priori as daily therapy on at least 4 of 6 visits requiring at least 500 mcg of fluticasone with or without a long-acting beta-agonist versus 100mcg or less of fluticasone, respectively.
Among 619 participants, 40.9% had difficult-to-control asthma, 37.5% had easy-to-control asthma, and 21.6% fell into neither group. Adherence to treatment was similar among the 3 groups. The phenotypes of difficult-to-control and easy-to-control asthma were stable over time and they also appeared to be distinctly evident from the start of the study. Over time, difficult-to-control asthma was characterized by high exacerbation rates, especially in the spring and fall; greater daytime and nocturnal symptoms, especially in the fall and winter; and compromised pulmonary physiology despite ongoing high-dose controller therapy. At baseline, FEV1 bronchodilator responsiveness was the most important characteristic that distinguished difficult-to-control asthma from easy-to-control asthma. Besides pulmonary physiology measures, Asthma Control Test score and markers of rhinitis severity and atopy were among other major discriminating features.
The authors concluded that despite good adherence, difficult-to-control asthma showed little improvement in symptoms, exacerbations or pulmonary physiology over the year. In addition, clinical characteristics, specifically bronchodilator responsiveness, Asthma Control Test, spirometry, rhinitis severity and atopy represent potential assessments that can be employed early in the course of treatment to identify children with difficult-to-control asthma.
The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.