Use of induced sputum to examine airway inflammation in childhood asthma,☆☆,

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Abstract

Airway inflammation is important in the pathogenesis of asthma, during which it may lead to symptomatic exacerbations and increases in asthma severity, as well as contribute to future decline in asthma status. The use of induced sputum has emerged as an important and useful technique to study airway inflammation. It has particular advantages in the study of childhood asthma because it is noninvasive and allows samples to be collected on repeated occasions in children over 7 years of age. The results of cell counts are reliable when the sputum is processed in a standardized manner involving selection from saliva, cell dispersion, and quantitative cytology. Children with asthma have increased eosinophils and mast cells, which may persist even with high doses of inhaled corticosteroid therapy. During a severe exacerbation of asthma, there is an intense and heterogeneous inflammatory response involving eosinophil and neutrophil accumulation and activation. Characterization of the relevance of airway inflammation in children with asthma is important. (J Allergy Clin Immunol 1998;102:S100-1.)

Section snippets

ASSESSMENT OF INFLAMMATION

Typically, airway inflammation has been assessed by bronchoscopic studies by means of biopsies, bronchial brushings, and bronchoalveolar lavage. A limited number of these studies have been conducted in children. They indicate that the presence of airway eosinophilia and mast cell activation correlates with airway hyperresponsiveness.3, 4 Bronchoscopy is comparatively invasive and of limited use to study large numbers of children with asthma on repeated occasions. Recently, the technique of

INDUCED SPUTUM IN CHILDHOOD ASTHMA

The results of induced sputum from normal children show that the predominant cell is the macrophage; eosinophils and mast cells are seldom seen. Eosinophils comprise less than 2.5% of cells in normal children.

In contrast, in children with stable asthma there are increased numbers of eosinophils and mast cells. There is a range of sputum eosinophil counts in children with stable asthma. The significance of this range has yet to be defined. It will be important to establish whether there is an

CONCLUSION

There is a need to conduct studies in children to establish the role of airway inflammation in childhood asthma. From these studies we may gain new insights into the pathogenesis of asthma that may not be possible from studies in adults. Research to date indicates that induced sputum is a suitable way to obtain airway secretions for the study of airway inflammation in childhood asthma. Eosinophils and mast cells form the characteristic inflammatory cell profile in stable childhood asthma, and

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From the Department of Respiratory Medicine, John Hunter Hospital, Newcastle.

☆☆

Reprint requests: Peter G. Gibson, MBBS, FRACP, Department of Respiratory Medicine, John Hunter Hospital, Locked Bag 1 Hunter Region Mail Centre, Lookout Rd, New Lambton Heights, New South Wales 2305, Australia.

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