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03-06-2010 | Respiratory | Article

Granulocytes from sputum help identify severe asthma

Abstract

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MedWire News: Inflammatory granulocytes from sputum identify asthma patients with different pathologies and clinical characteristics, US research shows.

Individuals with a high percentage of eosinophils and neutrophils have low lung function, worse asthma control, and increased use of healthcare resources, report Annette Hastie (Wake Forest University, Winston-Salem, North Carolina) and colleagues in the Journal of Allergy and Clinical Immunology.

They carried out a comprehensive analysis of induced sputum over a spectrum of asthma severity to help identify factors that characterize different asthma phenotypes.

Hastie and team enrolled 242 patients to a severe asthma clinical program. Individuals were stratified by sputum granulocytes (<2% or ≥2% eosinophils and <40% or ≥40% neutrophils). Those with increased eosinophils and neutrophils had the lowest lung function and increased symptoms and healthcare use.

As the researchers point out, patients with severe asthma have increased granulocytes in their sputum compared with patients with mild-to-moderate asthma. They suggest that inflammatory granulocytes in sputum may identify specific asthma severity phenotypes.

Individuals with a high eosinophil count, either with or without increased neutrophils had a significantly increased fraction of exhaled nitric oxide (FeNO), higher serum eosinophils, and a greater use of daily beta-agonists than those with lower levels.

Data from a microarray analysis also showed that up to 28 inflammatory proteins were significantly increased in the sputum with elevated neutrophils. Similarly, data stratified by sputum granulocytes showed that there were significant increases in brain-derived neurotrophic factor, interleukin-1b, and macrophage inflammatory protein 3a/CCL20 among patients with 40% neutrophils or more.

"Protein microarray screening of sputa identified novel proteins that have been less well recognized for participation in asthma and suggested a TH1 component to inflammation in more severe asthma," say Hastie and colleagues.

Approaches identifying cellular and biochemical proteomics can help provide a better understanding of the pathogenesis of asthma subphenotypes, and "may lead to development of biomarkers differentiating heterogeneity in asthma," conclude the researchers.

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