Sputum induction in children with asthma: a tertiary-center experience

Researching asthma across the ages: insights from the National Heart, Lung, and Blood Institute's Asthma Network

Clinical asthma studies across different age groups (ie, cross-age studies) can potentially offer insight into the similarities, differences, and relationships between childhood and adult asthma. The National Institutes of Health's Asthma Research Network (AsthmaNet) is unique and innovative in that it has merged pediatric and adult asthma research into a single clinical research network. This combination enhances scientific exchange between pediatric and adult asthma investigators and encourages the application of cross-age studies that involve participants from multiple age groups who are generally not studied together. The experience from AsthmaNet in the development of cross-age protocols highlights some of the issues in the evaluation of cross-age research in asthma. The aim of this review is to summarize these challenges, including the selection of parallel cross-age clinical interventions, identification of appropriate controls, measurement of meaningful clinical outcomes, and various ethical and logistic issues.

Predictors for failed dose reduction of inhaled corticosteroids in childhood asthma

BACKGROUND AND OBJECTIVE

Studies of Western populations have shown that increased exhaled nitric oxide (FeNO) and/or sputum eosinophils (sp-Eos) are predictive of asthma exacerbations. However, the utility of these measurements in different populations and settings is unknown. This study aimed to determine the predictors for failure of reduction of inhaled corticosteroid (ICS) doses in children with stable asthma.

METHODS

Fifty children (median age 11.8 years, interquartile range (IQR) 5.9 years) had their dose of ICS halved every 8 weeks until they reached the study end-point (exacerbation or weaned off ICS). Spirometry, FeNO and induced sputum cells were measured at baseline and at each stage of ICS reduction.

RESULTS

Eleven subjects suffered an asthma exacerbation and the remainder was successfully weaned off ICS. Subjects with an exacerbation were older (15.4 years (IQR 5.4) vs 11.4 years (IQR 3.9), P = 0.019) and more likely to be boys (P = 0.035). FeNO (median 156 p.p.b. (IQR 131) vs 76.1 p.p.b. (IQR 79.5), P = 0.013) and sp-Eos (17.3% (IQR 33.8%) vs 7.1% (IQR 9.9%), P = 0.019) were significantly greater in those who had an exacerbation. The areas under the receiver operating characteristic curves for FeNO (0.78, 95% CI: 0.59-0.97, P = 0.013) and sp-Eos (0.76, 95% CI: 0.56-0.96, P = 0.016) were similar (P = 0.88) and both were significantly greater than that for FEV(1)% predicted (0.12, 95% CI: 0.08-0.56, P = 0.0013).

CONCLUSIONS

Older boys with raised FeNO and sp-Eos are at higher risk of failure of reduction in their ICS dose. Monitoring airway inflammation in children with asthma using FeNO or sp-Eos is clinically useful in guiding ICS dose reduction in a non-Western outpatient setting.

Induced sputum inflammatory measures correlate with disease severity in children with obstructive sleep apnoea

OBJECTIVE

To establish the association between airway inflammation and severity of obstructive sleep apnoea (OSA) in children.

METHODS

Consecutive children presenting with symptoms suggestive of OSA were recruited. They completed a sleep apnoea symptom questionnaire, underwent physical examination, spirometry, sputum induction and an overnight polysomnography. Adequate sputum contained <50% squamous epithelial cells, and OSA was diagnosed if the obstructive apnoea index was >1.

RESULTS

73 children with a median (interquartile range (IQR)) age of 11.3 (10.0-13.2) years were recruited. There were 21 girls and the median body mass index of the group was 24.0 (18.0-27.0) kg/m2. The most common presenting symptoms were habitual snoring, mouth breathing and prone sleeping position. Sputum induction was successful in 43 (59%) children, of whom 14 were found to have OSA. Children with OSA had significantly greater percentage sputum neutrophil than those without OSA (18.5 (IQR 8.0-42.0) v 4 (IQR 3.0-11.3), p = 0.006). On multiple regression analysis, percentage sputum neutrophil was significantly associated with OSA (odds ratio = 1.1, p = 0.013).

CONCLUSION

Children with OSA had airway inflammation characterised by a marked increase in neutrophils. Further studies are needed to confirm these findings and to better define the downstream cellular interactions and molecular pathogenesis in childhood OSA.