Reproducibility in induced sputum in children with asthma

Abstract

In asthmatic children sputum-induction with hypertonic saline is useful to quantify the eosinophilic inflammation. However, only few data are available about feasibility and safety of the procedure in children. Therefore, taking 9 non-atopic healthy control children (mean age 11.8 years) and 34 asthmatic children (mean age 11.4 years), inhaling n = 25 Budesonid (400-1200 micrograms/die) and n = 9 DNCG (60 mg/die), sputum induction was performed twice within 6 weeks. Briefly, 10 minutes after inhalation of 200 micrograms salbutamol subjects inhaled hypertonic saline (3, 4 and 5%) for in all 30 minutes, while all 5 minutes lung function was checked and expectoration of sputum was supported. Adequate sputum plugs were separated from contaminating saliva and processed immediately employing native chamber and cytospin cell count as well as measurement of eosinophilic cationic protein (ECP). Sputum-induction could be performed in 84 out of 86 planed tests (97.7%) without any objective clinical adverse effects. The mean fall in FEV1 was 3.0%, the maximum 11.0%. The reproducibility of eosinophil, neutrophil and lymphocyte differential cell count (5-95%-values Test1: 0.0-4.2%, 0.8-11.4%, and 3.2-35.1%, respectively) was moderate for eosinophils and neutrophils (Intraclass-Correlation-Coefficient (ICC) 0.41) as well as for lymphocytes (ICC = 0.49). For ECP 5-95%-values Test1: 39.8-8000.0 micrograms/l) only a fair reproducibility (ICC = 0.24) was found. The ICC levels for total cell count (ICC = 0.31) and for weight of the sputum plug (ICC = 0.30) were also fair. Based on the procedure presented induced sputum is a feasible and safe method in childhood. The differential sputum cell count of eosinophils, neutrophils and lymphocytes can be recommended as parameters with moderate reproducibility.