Supplementary Material for: Eosinophil-derived neurotoxin is an asthma biomarker linked to wheezing severity in preschool children

Background
Novel biomarkers are needed for understanding the clinical characteristics of children with acute wheeze (AW) and for optimizing management strategies. This study investigated serum eosinophil-derived neurotoxin (EDN) and blood eosinophil count (B-Eos) in Japanese pre-school children with current asthma (CA) and/or AW.
Methods
Two cohorts of Japanese children under 6 years of age were screened for allergy and asthma symptoms using the ISAAC questionnaire and tested for EDN, B-Eos and specific IgE. Cohort 1 included 16 children with CA, 45 with other allergies (OA), e.g. eczema or rhinitis, and 34 healthy controls (HC). Optimal cut-offs (receiver operating characteristic analysis) for EDN and B-Eos were determined for CA vs HC. Cohort 2 included 87 children with AW grouped according to symptom severity, high (EDN-H, B-Eos-H) or low (EDN-L, B-Eos-L) EDN and B-Eos (using the optimal cut-offs) and were followed up during recovery.
Results
Children with CA or OA had higher EDN vs HC (p<0.01). The B-Eos was higher in CA vs HC (p<0.05). The optimal cut-offs for EDN and B-Eos were 26.5 µg/L and 235 cells/µL, respectively. EDN was higher in wheezing children with severe vs mild or moderate symptoms (p<0.05). Conversely, B-Eos were higher in children with mild vs moderate symptoms (p<0.01). EDN decreased in the EDN-H group between AW and recovery (p<0.001). Higher EDN, and to a lesser extent, B-Eos were associated with IgE sensitization.
Conclusion
Serum EDN is a promising exploratory biomarker for CA and AW in pre-school children associated with wheezing severity and recovery after treatment.