New research indicates that asthma in many adolescents is not likely to involve inflammation of the airways and therefore should not be considered an allergic disease.
For the study, investigators assessed clinical characteristics and inflammatory markers in 77 adolescents with asthma and compared them with those found in 68 healthy participants aged 12 to 17 years. The presence of asthma did not appear to involve eosinophils or neutrophils, specific types of white blood cells that are present in higher concentrations in response to inflammation.
“These findings are important since current treatment is largely directed at reducing inflammation and may explain why in some asthmatics, asthma medication is less effective,” said Dr Jeroen Douwes, professor of public health and director of Massey University’s Centre for Public Health Research (CPHR) in Wellington, New Zealand and senior author of the study. “If asthma can occur without any airway inflammation then other treatments may need to be developed for those asthmatics.”
Background and objective
Neutrophilic inflammation has been implicated in non-eosinophilic asthma (NEA) in adults, but little is known about NEA in children/adolescents. We assessed clinical and inflammatory characteristics of NEA in adolescent asthma.
Airway inflammation, sputum endotoxin, airway hyper-reactivity, atopy and lung function were assessed in 77 adolescents with asthma and 68 without asthma (12–17 years). Asthma was identified on the basis of wheeze and asthma history.
The proportion of NEA (sputum eosinophils <2.5%) was 54%. In this group, atopy, sputum neutrophil, eosinophil, eosinophil cationic protein (ECP), endotoxin, neutrophil elastase and IL-8 levels were not different from those without asthma. In contrast, eosinophilic asthma (EA) was associated with atopy and sputum ECP and IL-8. The majority of NEA had no evidence of inflammation; only 14% had neutrophilia (≥61% neutrophils), compared with 11% of EA, and 15% of those without asthma. Small differences in FEV1 (NS) were found between EA and NEA, but symptom prevalence and severity was not different (63% of EA and 52% of NEA were classified moderate to severe).
NEA is common in adolescent asthma and has similar clinical characteristics as EA. Neutrophils do not appear to play a role in NEA in adolescents, and underlying mechanisms may not involve airway inflammation.