Elevated ACE levels have been linked to endothelial dysfunction, inflammation, and vascular remodelling, all of which are implicated in the pathogenesis of CAD.43,44 Several studies have reported a positive correlation between ACE levels and CAD incidence or severity.45 Additionally, ACE inhibitors, which block the action of ACE, have shown beneficial effects in CAD management, further highlighting the potential utility of ACE as a CAD biomarker.46 Haptoglobin is an acute-phase protein that binds free haemoglobin to prevent oxidative damage and facilitate its clearance. Here, ACE is linked to endothelial dysfunction.