Sputum Induction in Children and Adolescents with Problematic Severe Asthma: Success Rate, Safety and Tolerability

Background: In problematic severe asthma (PSA), inflammatory phenotypes can by identified by assessing cel- lularity in induced sputum (IS) samples. However, there have been few studies employing sputum induction (SI) in pedi- atric patients. Objective: To assess the success rate, safety and tolerability of SI, as well as IS sample cellularity, in pediatric PSA pa- tients. Methods: We conducted a cross-sectional study involving 44 pediatric PSA patients. We collected IS samples using inha- lations of nebulized saline solution. On the basis of the post-bronchodilator forced expiratory volume in one second (FEV1, % of predicted), we administered nebulization with 4.5% hypertonic saline (for patients with an FEV1 � 60%) or 0.9% isotonic saline (for those with an FEV1 50%. Results: The observed success rate was 75% (95% CI: 60-86). Most of the patients provided satisfactory samples, al- though multiple SI sessions were required in some cases (27%). In comparison with the IS samples containing > 20% squamous cells, those containing � 20% showed significantly more neutrophils (P = 0.02) and eosinophils (P = 0.03). The most common adverse events were mild wheezing (in 14%) and salty taste (in 9%). In 8% of the sessions, there was a � 20% decrease in FEV1. Conclusion: In our sample of pediatric patients with PSA, sputum induction was safe and generally well tolerated, sug- gesting that it could be useful in the assessment of inflammatory processes in such patients.