Obstruction phenotype as a predictor of asthma severity and instability in children

Publication date: Available online 14 November 2017
Source:Journal of Allergy and Clinical Immunology
Author(s): Ronald L. Sorkness, Edward M. Zoratti, Meyer Kattan, Peter J. Gergen, Michael D. Evans, Cynthia M. Visness, Michelle Gill, Gurjit K. Khurana Hershey, Carolyn M. Kercsmar, Andrew H. Liu, George T. O'Connor, Jacqueline A. Pongracic, Dinesh Pillai, Christine A. Sorkness, Alkis Togias, Robert A. Wood, William W. Busse
BackgroundSmall airways instability, resulting in premature airway closure, has been recognized as a risk for asthma severity and poor control. Although spirometry has limited sensitivity for detecting small airway dysfunction, a focus on the air-trapping component of obstruction may identify a risk factor for asthma instability.ObjectiveTo use spirometric measurements to identify patterns of airway obstruction in children, and define obstruction phenotypes that relate to asthma instability.MethodsPre- and post-bronchodilation spirometry data were obtained from 560 children in the Asthma Phenotypes in the Inner City study. An air-trapping obstruction phenotype (A Trpg) was defined as forced vital capacity (FVC) Z-score < -1.64, or an increase of FVC ≥ 10% predicted with bronchodilation. The airflow limitation phenotype (A Limit) had forced expiratory volume in 1 s (FEV1)/FVC Z-score < -1.64, but not A Trpg. The None phenotype had neither A Trpg nor A Limit. The 3 obstruction phenotypes were assessed as predictors of number of exacerbations, asthma severity, and airway lability.ResultsThe A Trpg phenotype (14% of the cohort) had more exacerbations during the 12-month study, compared with the A Limit (P<0.03) and the None (P<0.001) phenotypes. The A Trpg phenotype also had the highest Composite Asthma Severity Index, the highest asthma treatment step, the greatest variability in FEV1 over time, and the greatest sensitivity to methacholine challenge.ConclusionsA Trpg and A Limit patterns of obstruction, defined with routine spirometric measurements, can identify obstruction phenotypes that are indicators of risk for asthma severity and instability.



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