A serum amyloid A and LDL complex as a new prognostic marker in stable coronary artery disease

Background: Although some reports have indicated that acute phase proteins such as C-reactive protein (CRP) and serum amyloid A (SAA) can predict the prognosis in patients with acute coronary syndrome, the value of these markers in patients with stable coronary artery disease (CAD) still remains obscure. Therefore, our aim was to determine the prognostic value of inflammatory markers in patients with stable coronary artery disease. Methods and results: We conducted a prospective cohort study in 140 consecutive patients with stable coronary artery disease who had at least one coronary stenosis more than 50% in diameter seen on diagnostic coronary angiography (CAG). We determined serum levels of the SAA/LDL complex as a new marker in addition to CRP and SAA. Serum levels of the SAA/LDL complex were measured by a sandwich enzyme-linked immunosorbent assay (ELISA). End-points were defined as cardiac death, myocardial infarction, cerebral infarction, and coronary revascularization. End-point events occurred in 21 patients (2 death from myocardial infarction, 2 cerebral infarction, and 17 revascularization). Age (year) (OR=1.14, CI: 1.05–1.25), diabetes mellitus (OR=3.50, CI: 1.08–11.40), triglyceride (10 mg/dl) (OR=1.12, CI: 1.01–1.23) and SAA/LDL complex (10 μg/ml) (OR=2.32, CI: 1.05–4.70) were independently related to the events. A reconstitution experiment suggested that the SAA/LDL complex is derived by oxidative interaction between SAA and lipoproteins. Conclusions: The SAA/LDL complex reflects intravascular inflammation directly and can be a new marker more sensitive than CRP or SAA for prediction of prognosis in patients with stable coronary artery disease.