Combined assessment of serum eosinophil-derived neurotoxin and YKL-40 may identify Asthma-COPD overlap.

Background: We previously showed that the proportion of patients with both high serum periostin and YKL-40 levels was significantly higher in asthma-COPD overlap (ACO) than in asthma or COPD (Odds ratio, 2.59: JACI Pract 2019). In this study, we hypothesised that using serum eosinophil-derived neurotoxin (EDN) instead of periostin would be useful to identify ACO. Aims: To assess the usefulness of combined assessment of serum EDN and YKL-40 in identifying ACO. Methods: Subjects included Japanese patients with asthma (n = 177), ACO (n = 115), or COPD (n = 61). Serum EDN, YKL-40, and total IgE, blood eosinophils, and FeNO were measured and compared among the patients. Results: Serum EDN was higher in ACO than in asthma or COPD, whereas serum YKL-40 was higher in both COPD and ACO than in asthma (Figure 1A). Serum EDN levels weakly correlated with serum YKL-40 levels in COPD, but not in asthma and ACO. Multivariate linear regression analysis revealed that higher eosinophil counts and higher YKL-40 levels were significantly associated with higher EDN levels. Based on cutoff values derived by ROC analysis (EDN: 23.0 ng/mL; YKL-40: 61.3 ng/mL), patients were classified into high or low groups. The proportion of patients with both high serum EDN and YKL-40 levels was significantly higher in ACO than in asthma or COPD (odds ratio, 3.85 (95% CI, 2.35-6.36); p Conclusions: Combined assessment of serum EDN, rather than periostin, and YKL-40 may identify ACO.