• Christopher Newby, Joshua Agbetile, Beverley Hargadon, Will Monteiro, Ruth Green, Ian Pavord, Christopher Brightling, and Salman Siddiqui.
• Department of Health Sciences, University of Leicester, Leicester, United Kingdom.
• J. Allergy Clin. Immunol. 2014 Aug 1;134(2):287-94.

BackgroundEosinophilic airway inflammation measured by using induced sputum is an important treatment stratification tool in patients with severe asthma. In addition, sputum eosinophilia has been shown to be associated with severe exacerbations and airflow limitation.ObjectivesWe sought to identify whether eosinophilic inflammation in sputum is associated with FEV₁ decrease in patients with severe asthma and whether we could identify subgroups of decrease behavior based on the variation of eosinophilic airway inflammation over time.MethodsNinety-seven patients with severe asthma from the Glenfield Asthma Cohort were followed up with scheduled 3-month visits; the median duration of follow-up and number of visits was 6 years (interquartile range, 5.6-7.6 years) and 2.7 visits per year. Induced sputum was analyzed for eosinophilic inflammation at scheduled visits. Linear mixed-effects models were used to identify variables associated with lung function and overall decrease. In addition, using individual patients' mean and SD sputum eosinophil percentages over time, a 2-step cluster analysis was performed to identify patient clusters with different rates of decrease.ResultsFEV₁ decrease was -25.7 mL/y in the overall population. Postbronchodilator FEV₁ was also dependent on exacerbations, age of onset, height, age, sex, and log10 sputum eosinophil percentages (P < .001). Three decrease patient clusters were identified: (1) noneosinophilic with low variation (mean decrease, -14.0 mL/y), (2) eosinophilic with high variation (mean decrease, -40.9 mL/y), and (3) hypereosinophilic with low variation (mean decrease in lung function, -19.2 mL/y).ConclusionThe amplitude of sputum eosinophilia was associated with postbronchodilator FEV₁ in asthmatic patients. In contrast, high variability rather than the amplitude at baseline or over time of sputum eosinophils was associated with accelerated FEV₁ decrease.Copyright © 2014 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.

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