Moving Beyond LDL-C and Non-HDL-C: Apolipoprotein B as the Stronger Lipid-Related Predictor of Coronary Artery Disease in Statin-Treated Patients

<b>Background/Objectives:</b> Coronary artery disease (CAD) remains the leading cause of death primarily in patients over 65 years old, with an increasing incidence, especially in Eastern European countries. Primary and secondary prevention protocols are based on a large number of cardiovascular (CV) risk factors, but low-density lipoprotein cholesterol (LDL-C) remains the main treatment target and one of the central determinants of CV risk. Apolipoprotein B (apoB) is the main structural protein in all atherogenic lipoproteins, and, unlike LDL-C, which only reflects the cholesterol content of LDL, apoB directly quantifies the total number of all circulating atherogenic particles. Over the past decade, a growing amount of data has supported the utility of apoB for CV risk assessment; however, its superiority over LDL-C remains unclear. Our study aimed to investigate the predictive value of apoB for both the presence and the severity of CAD in a statin-treated cohort from an Eastern European hospital and to compare it with standard lipid biomarkers. <b>Methods:</b> A total of 121 statin-treated patients, who were evaluated using coronary angiography, were consecutively enrolled and subdivided into three groups: 52 patients with significant coronary artery disease (S-CAD), 36 patients with non-significant coronary artery disease (NS-CAD), and 33 patients without coronary atherosclerosis (N-CAD). Apolipoprotein B was measured at the moment of enrollment using the immunoturbidimetric assay. <b>Results:</b> The mean values of LDL-C, TC, non-HDL-C, and apoB increased progressively across the three studied groups. Unlike traditional lipid biomarkers, apoB levels differed significantly not only between N-CAD and S-CAD, but also between N-CAD and NS-CAD. The diagnostic superiority of apoB extended beyond group mean differences, as it also demonstrated the strongest correlation with CAD severity. ApoB showed a moderate correlation with the Gensini score (r = 0.43, <i>p</i> < 0.001), which was markedly higher compared to LDL-C, TC, or non-HDL-C, all of which presented only a weak correlation (r = 0.26, r = 0.23, and r = 0.28, respectively). Additionally, in a logistic regression analysis, apoB demonstrated the highest predictive power for the presence of significant CAD (per SD increase: OR 2.386, 95% CI 1.52-3.75, <i>p</i> = 0.000), and it was the only biomarker able to predict left main disease (per SD increase: OR 2.433, 95% CI 1.38-4.30, <i>p</i> = 0.002) and three vessel disease (per SD increase: OR 1.639, 95% CI 1.012-2.654, <i>p</i> = 0.044). Residual apoB was also calculated and remained significantly associated with the presence of coronary atherosclerosis. <b>Conclusions:</b> ApoB proved to be a reliable predictor for CAD, independent of LDL-C. Compared to standard lipid biomarkers, apoB was superior in detecting NS-CAD and showed a better correlation with the severity of CAD. Additionally, in our study, only apoB was significantly correlated with left main disease and three vessel disease.