Serum EDN as a novel biomarker for severe eosinophilic adult asthma

Eosinophilic inflammation is a major pathophysiological mechanism in severe asthma (SA). However, a reliable serum biomarker reflecting this type of inflammation has not yet been identified. Therefore, in this study, we aimed to investigate whether serum levels of eosinophil-derived neurotoxin (EDN) could serve as a biomarker for predicting the diagnosis of SA in adult patients with asthma.

A total of 89 patients, including 52 with SA and 37 with nonsevere asthma (NSA), were included in the study, all having PBEC ≥ 150 cells/µL. The relationships between serum EDN and serum eosinophilic cationic protein (ECP) levels with peripheral blood eosinophil count (PBEC), as well as with clinical and demographic parameters, were assessed. In addition, the clinical validity of serum EDN and PBEC levels in predicting the SA phenotype was evaluated.

A correlation analysis among PBEC, serum EDN, and serum ECP levels revealed statistically significant positive correlations: between PBEC and serum ECP (p<0.001), PBEC and serum EDN (p<0.001), and serum ECP and serum EDN (p=0.002). Serum EDN and PBEC levels were significantly higher in the SA group compared to the NSA group (225.40 [0.001-588.76] vs. 380.05 [0.001-1920.45], p<0.001; 290 [160-820] vs. 335 [170-2070], p=0.003, respectively). Regarding spirometric parameters, FEV₁ (mL and %), FVC (mL and %), and FEF_25-75 (mL and %) values were significantly lower in the SA group compared to the NSA group. In the receiver operating characteristic (ROC) curve analysis evaluating the predictive value of serum EDN levels for identifying the SA phenotype, a sensitivity of 69% was observed. In univariate analysis, both serum EDN and PBEC levels were significantly associated with SA. However, multivariate analysis demonstrated that only serum EDN levels remained a statistically significant independent predictor of the SA phenotype.

Serum EDN emerged as an independent predictor of the SA phenotype and demonstrated superior diagnostic performance compared with conventional eosinophilic markers. These findings highlight its potential as a promising biomarker for identifying SA and reflecting underlying type 2 airway inflammation.