title: Sputum induction in children with difficult asthma: safety, feasibility, and inflammatory cell pattern.
abstract: Difficult childhood asthma is defined by persistent symptoms despite maximal conventional therapy. We aimed to establish a safe method of sputum induction for these children and to study cytology and the relationship to exhaled nitric oxide (eNO). Sputum induction was performed in 38/40 children (aged 6-16 years) with difficult asthma, using 3.5% saline for four 5-min periods after bronchodilator pretreatment. Two children were excluded from sputum induction because postbronchodilator forced expired volume in 1 sec (FEV(1)) was <65% predicted. Seven of 38 children had symptoms (dyspnea and wheezing) during induction; of these, 3 experienced a fall in FEV(1) of >20% from postbronchodilator FEV(1), readily reversed with salbutamol. Sputum induction was successful in 28/38 children, with a higher success rate in children >/= 12 years than in younger children (87% vs. 50%, P = 0.02). Only 9/28 had abnormal sputum cytology; of these, 6 had predominant sputum eosinophilia (>2.5% eosinophils, </=54% neutrophils), while 3 had sputum neutrophilia (</=2.5% eosinophils, >54% neutrophils). Of 23 children with elevated eNO values, only 6 had sputum eosinophilia. In conclusion, sputum induction can be used to assess airway inflammation in children with difficult asthma, but abnormal sputum cytology is only present in a minority. Raised nitric oxide is only poorly predictive of sputum eosinophilia in these children.
authors.affiliation: Department of Respiratory Paediatrics, Royal Brompton Hospital, London, UK.
authors.forename: Christiane
authors.initials: C
authors.lastname: Lex
authors.forename: Donald N R
authors.initials: DN
authors.lastname: Payne
authors.forename: Angela
authors.initials: A
authors.lastname: Zacharasiewicz
authors.forename: Albert M
authors.initials: AM
authors.lastname: Li
authors.forename: Nicola M
authors.initials: NM
authors.lastname: Wilson
authors.forename: Trevor T
authors.initials: TT
authors.lastname: Hansel
authors.forename: Andrew
authors.initials: A
authors.lastname: Bush
mesh_terms: D000293:Adolescent; D001249:Asthma / Q000175:diagnosis*; D002648:Child; D004804:Eosinophils / Q000166:cytology; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D007249:Inflammation / Q000276:immunology; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D013048:Specimen Handling; D013147:Spirometry; D013183:Sputum / Q000166:cytology*
chemical_list: D009569:Nitric Oxide