A study of children with severe therapy-resistant asthma found that eosinophil counts in their lavage and biopsy specimens were significantly elevated compared with those in control subjects.
The study comprised 69 children aged 5 to 16 years at a London hospital and was conducted from April 2005 to June 2009. Of the participants, 53 exhibited severe therapy-resistant asthma (STRA); 16 were nonasthmatic control subjects.
The investigators’ goal was to support their theory that children with STRA exhibited airway eosinophilia and mast cell inflammation, which they suspected was triggered by the TH2 cytokines IL-4, IL-5, and IL-13.
All study participants received a bronchoscopy under general anesthesia as well as a bronchoalveolar lavage (BAL) and endobronchial biopsy. The control subjects were in the hospital for unrelated reasons but agreed to allow extra samples to be taken for the purposes of this study.
Of 121 biopsy specimens taken from the 69 participants, only one child in the control group had a specimen that was insufficient for evaluation. Fifty of the 53 BAL specimens from children with STRA and 14 of the 16 control subjects’ BAL specimens were suitable for analysis.
Contrary to the researchers’ hypothesis, the TH2 cytokines were not the cause of allergic asthma in children and were nearly undetectable in the BAL fluid of most of the STRA subjects.
“We have shown that, unlike in adults, STRA in children is characterized by eosinophilic and not neutrophilic airway inflammation,” researchers wrote. “This report highlights there might be different mechanisms driving pediatric as opposed to adult STRA and carries the implication that successful adult therapeutic strategies should not be uncritically extrapolated to children.”