Sputum eosinophils are a strong predictor of airway inflammation and exacerbations. Sputum neutrophils indicate a different severe asthma phenotype that is potentially less responsive to TH2-targeted therapy such as inhaled corticosteroids.
This U.S.-based Wake Forest Severe Asthma Research Program included 328 patients with asthma. Blood eosinophil counts, FeNO levels, and total IgE levels did not accurately predict sputum eosinophil percentages. Age, FEV1 percent predicted, and blood neutrophil counts were similarly unsatisfactory for the prediction of sputum neutrophil percentages.
FeNO levels, IgE levels, blood eosinophil and neutrophil counts, FEV1, and age are poor surrogates for predicting sputum eosinophil and neutrophil percentages.
Biomarker surrogates do not accurately predict sputum eosinophil and neutrophil percentages in asthmatic subjects. Annette T. Hastie et al. The Journal of Allergy and Clinical Immunology, Volume 132, Issue 1 , Pages 72-80.e12, July 2013.
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