High-sensitive cardiac troponin I (hs-cTnI) is a recognized marker of myocardial injury in acute coronary syndromes, but its utility in chronic coronary syndromes (CCS) remains unclear. Midkine (MK), a heparin-binding growth factor, plays a role in inflammation and vascular remodeling in atherosclerosis. This cross-sectional study aimed to evaluate the predictive value of serum hs-cTnI and MK in determining the severity of coronary artery obstruction in patients with CCS. The study included 125 subjects undergoing coronary angiography (CAG) at the Iraqi Center of Heart Disease/ Medical City/Baghdad, from March to December 2024. Subjects were classified into three groups based on CAG findings: no CAD, 1- or 2-vessel disease, and 3-vessel or left main disease. Serum levels of hs-cTnI and MK were measured using enzyme-linked immunosorbent assay (ELISA) in the laboratories of Department of Biochemistry/College of Medicine/ Baghdad University. Median serum levels of both biomarkers differed significantly across all groups. Receiver operating characteristic curve analysis demonstrated good diagnostic performance for both biomarkers in differentiating moderate (Group II) from severe disease (Group III). For hs-cTnI, a cutoff of 354.4 pg/mL yielded 90% sensitivity and 92% specificity; for MK, a cutoff of 2.75 ng/mL yielded 90% sensitivity and 85% specificity. Logistic regression revealed that the two biomarkers together explained 75% of the variance in CAD severity. Combining the two markers offered a slight improvement in diagnostic accuracy compared to using either alone. In conclusion, serum hs-cTnI and MK levels may help predict CAD severity in CCS and support early risk stratification before CAG.
