Importantly, ROC analysis demonstrated that plasma kallistatin discriminates stable COPD from healthy controls with an AUC of 0.788 (95% CI, 0.688–0.888; p < 0.001) and exacerbations from health with an AUC of 0.853 (95% CI, 0.771–0.936; p < 0.001), indicating fair-to-good diagnostic accuracy and potential clinical utility pending multicenter validation. Here, SERPINA4 is linked to chronic obstructive pulmonary disease.