Development and clinical application of a sensitive enzyme-linked immunosorbent assay for neutrophil elastase as a serum biomarker of myocardial infarction

BACKGROUND: Neutrophil elastase (NE) is a serine protease involved in inflammation and tissue remodeling, but its potential as a serum biomarker for myocardial infarction (MI) remains incompletely characterized, partly due to the lack of highly sensitive and specific detection tools. METHODS: We developed a sensitive NE ELISA kit and evaluated it in 103 MI patients and 42 healthy controls. Receiver operating characteristic (ROC) curve analysis and partial correlation analysis were performed to evaluate the diagnostic and predictive performance of serum NE. RESULTS: Our NE ELISA kit achieved a detection limit as low as 5 pg/mL, demonstrating higher sensitivity than the commercial kit while maintaining excellent specificity with minimal cross-reactivity against cathepsin G. A remarkably strong positive correlation was observed between our kit and the commercial kit (r = 0.96, p < 0.0001), confirming its reliability. Serum NE levels were significantly elevated in MI patients compared with healthy controls (p < 0.001). ROC curve analysis revealed that serum NE alone had good discriminatory power for MI (AUC = 0.9108, p < 0.0001), and combining NE with age further improved predictive performance (AUC = 0.9644, p < 0.0001). After age adjustment, serum NE remained significantly and positively correlated with cardiac troponin I (cTnI, r = 0.2604, p = 0.0132) and low-density lipoprotein cholesterol (LDL-c, r = 0.2303, p = 0.0233). CONCLUSION: These findings establish our NE ELISA kit as a valuable diagnostic tool and identify serum NE as a promising non-invasive biomarker for early risk assessment of myocardial infarction.