Association of EDN levels in patients with asthma and correlation with FEV₁%: A meta-analysis

Background: Eosinophil-derived neurotoxin (EDN), an eosinophil degranulation product, is a good biomarker for eosinophilic inflammation of the airway. Several articles have shown that EDN levels are higher in patients with asthma than in controls, and EDN levels are correlated with the percentage of predicted forced expiratory volume in the first second (FEV₁%) in patients with asthma. Their results were inconclusive. Methods: A comprehensive meta-analysis was performed to assess EDN levels between patients with asthma and controls, and the correlations between EDN and FEV₁% in the patients with asthma. Fourteen relevant articles were identified from electronic data bases. Pooled standardized mean difference (SMD) with a 95% confidence interval (CI) for the difference of EDN levels between the patients with asthma and controls, and pooled coefficient (r) values with 95% CI for the correlations between EDN and FEV₁%, respectively, were calculated. Results: A total of 14 articles were selected. Among the included reports, six articles related to the difference and eight essays on the correlation. Pooled effect size showed that EDN levels were higher in patients with asthma than in controls (SMD 2.85 [95% CI, 1.92-3.78]). Furthermore, the pooled effect size showed that EDN levels were negatively correlated with FEV₁% in patients with asthma (r -0.21 [95% CI, -0.28 to -0.14]). Conclusion: EDN levels increased in the patients with asthma compared with in the controls. They were correlated with FEV₁% in the patients with asthma, which indicated that EDN could be a reliable marker to monitor asthma's therapeutic effects.