Low-density lipoprotein (LDL), which includes apolipoprotein A-I (apoAI-LDL) as a novel marker of coronary artery disease

Background: Serum low-density lipoprotein (LDL), which includes apolipoprotein A-I (apoAI-LDL) may be generated by oxidization in the serum of patients with coronary artery disease (CAD). We determine the utility of the serum apoAI-LDL level as a novel coronary risk factor. Methods: We measured serum apoAI-LDL in 473 consecutive patients who underwent diagnostic coronary angiography. Serum levels of apoAI-LDL were assayed by a newly developed ELISA. Results: The patients consisted of 84 with unstable angina (UA), 259 with stable CAD, and 130 without CAD (control). The serum level of apoAI-LDL was higher in CAD patients than in the control group (31.4 (22.1-41.4) μg/ml vs. 24.6 (18.4-29.2) μg/ml, respectively, p < 0.001), as well as in patients with UA compared to those with stable CAD 44.5 (35.8-51.9) μg/ml vs. 27.1 (19.5-35.6) μg/ml, respectively, p < 0.0001) (data are expressed as the median (25th-75th percentiles)). By logistic regression analysis, only apoAI-LDL was independent, being significantly able to predict CAD (odds ratio: 1.50, 95% CI: 1.23-1.82, p < 0.001), and differentiate unstable angina (odds ratio: 1.80, 95% CI: 1.48-2.17, p < 0.001) after controlling for classical risk factors. Conclusion: The serum level of apoAI-LDL, a newly identified component of oxidized LDL, may be a more sensitive marker of CAD and acute coronary syndrome than CRP.