Comparison between eosinophilic markers in induced sputum and blood in asthmatic patients

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Abstract
Background: The usefulness and safety of the analysis of blood inflammatory markers in asthma are widely recognized. Recently, the analysis of induced sputum has been proposed as a safe, non‐invasive tool in the study of airway inflammation in asthma.Objective: Our aim was to test whether sputum analysis is more useful than blood analysis in the evaluation of airway inflammation in untreated and treated asthmatic patients.Methods: Twelve untreated patients with mild to moderate asthma underwent a methacholine challenge test, sputum induction and blood sampling. A group of 14 normal subjects was also evaluated for baseline comparison. The same evaluation was repeated after 3 months of budesonide treatment. Before and after treatment, we tested the relationship of eosinophilic markers in induced sputum and blood with clinical and functional data. We also compared eosinophilic markers in induced sputum with the same markers in blood.Results: Untreated patients showed a significant relationship between sputum eosinophils and symptom score, and between sputum eosinophilic cationic protein and symptom score, FEV1 and PD20FEV1. No relationship between blood eosinophilic markers and clinical or functional data was observed. In budesonide‐treated patients, both sputum and blood eosinophils were significantly lower than in untreated patients, but eosinophil decrease was greater in sputum than in blood. Sputum eosinophilic proteins were also significantly lower in treated patients, whereas serum eosinophilic proteins were low at baseline and remained unchanged after treatment. Sputum eosinophilic markers were lower in normal subjects than in both untreated and treated patients, while blood eosinophils, but not serum eosinophilic cationic protein, were lower in normals than in untreated patients.Conclusions: The analysis of induced sputum is more useful than the analysis of blood in the evaluation of asthma severity and of the effect of glucocorticoid treatment in patients with mild to moderate asthma.

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