Serum eosinophil-derived neurotoxin (EDN) may help identify the severity of asthma in adults, according to a Korean study published in Allergy, Asthma and Immunology Research.

Researchers conducted a study to analyze the association of serum EDN with eosinophil-related clinical parameters such as total eosinophil count (TEC) and serum periostin level in severe asthma (SA) vs non-severe asthma (NSA). A total of 1133 adults with asthma, including SA (n=898) and NSA (n=235), were enrolled along with normal controls (NCs) (n=125). Those with concurrent respiratory diseases were excluded. Asthma was diagnosed according to the Global Initiative for Asthma guideline. The patients were classified into the SA and NSA groups by the International European Respiratory Society/American Thoracic Society guidelines on severe asthma.

Serum levels of EDN were measured using 2 enzyme-linked immunosorbent assay (ELISA) kits: one that was already in use from MBL International and the new K-EDN kit from SKIMS-BIO Co. Measurements were taken as per manufacturer’s protocol. Serum periostin levels were measured simultaneously using an ELISA kit from Shino-Test.

Significant differences were found in TEC or sputum eosinophil count between the SA and NSA groups (P <.05). Also, a significant correlation was found between serum EDN levels measured by the 2 kits (ρ=0.545, P <.0001). However, correlation coefficients between serum EDN levels measured by the K-EDN kit and TEC were higher (ρ=0.358, P <.0001) than those between serum EDN levels measured by the MBL kit and TEC (ρ=0.319, P <.0001) or serum periostin level (ρ=0.222, P <.0001). Multivariate regression analysis showed that serum EDN levels measured by the K-EDN kit predicted the phenotype of SA (P =.003), which the other biomarkers did not.

Limitations of this study were that it was a cross-sectional study in a single center. Even though the number of patients was not small, replicated experiments are needed to enhance and consolidate the hypothesis. It was difficult to control medications used that could have affected the eosinophilic inflammation status. Also, further studies are needed to explore the exact function of EDN and other inflammatory mechanisms other than eosinophilic inflammation in the pathogenesis of SA.

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This study proves that the serum EDN level can help identify SA in adults, and that “[c]onsidering that SA has heterogeneous phenotypes, further studies are needed to identify useful biomarkers for assessing subtypes and long-term clinical outcome of SA.”

Reference

Lee Y, Lee JH, Yang EM, et al. Serum levels of eosinophil-derived neurotoxin: a biomarker for asthma severity in adult asthmatics. Allergy Asthma Immunol Res. 2019;11(3):394-405.