A-030 LDL-C and Apolipoprotein B Concordance Across Different Thresholds: Impact of Hypertriglyceridemia in a Real-World Laboratory Cohort

Abstract

Low-density lipoprotein cholesterol (LDL-C) remains the primary target for cardiovascular risk reduction; however, it reflects cholesterol content rather than the total number of circulating atherogenic particles. Apolipoprotein B (ApoB), present in one copy per atherogenic lipoprotein particle, more directly represents atherogenic burden. ACC/AHA guidelines recognize ApoB 130 mg/dL or higher as a risk-enhancing factor, particularly in individuals with elevated triglycerides (TG), in whom LDL-C may underestimate cardiovascular risk. We evaluated LDL-C/ApoB concordance in a large Brazilian laboratory population and assessed the impact of hypertriglyceridemia on discordance patterns. This cross-sectional study analyzed retrospective laboratory data from a private diagnostic center in Fortaleza, Brazil. Adults 18 years or older with concomitant LDL-C, ApoB, and TG measurements between 2021 and 2025 were included (n=14,940). LDL-C was calculated using the Friedewald formula. Lipids were measured using standardized enzymatic assays (Siemens), ApoB by immunoturbidimetry (Siemens), and HbA1c by high-performance liquid chromatography (Bio-Rad). LDL-C/ApoB concordance was evaluated using (i) manufacturer reference intervals and (ii) ACC/AHA guideline-based thresholds (LDL-C 160 mg/dL or higher; ApoB 130 mg/dL or higher). Agreement was assessed using Cohen’s kappa (k). Multivariable logistic regression examined associations between TG strata (<150, 150–199, 200 mg/dL or higher) and ApoB 130 mg/dL or higher or LDL-C/ApoB discordance, adjusting for age, sex, diabetes, and statin use. Sensitivity analysis excluded TG 400 mg/dL or higher. Mean LDL-C was 118.0 mg/dL, mean ApoB 87.0 mg/dL, and median TG 84 mg/dL. Under manufacturer criteria, LDL-C 130 mg/dL or higher occurred in 34.5% and ApoB above the sex-specific upper limit in 1.12%, with overall concordance of 66.3% and low agreement ( k = 0.041). Using ACC/AHA thresholds, LDL-C 160 mg/dL or higher occurred in 12.73% and ApoB 130 mg/dL or higher in 4.54%, yielding 91.4% concordance and moderate agreement (k = 0.466). Primary discordance (ApoB 130 mg/dL or higher with LDL-C <160 mg/dL) was uncommon (0.21%, 32/14,940) but concentrated in hypertriglyceridemia: 47% of discordant individuals had TG 200 mg/dL or higher. ApoB 130 mg/dL or higher increased progressively across TG strata (2.84% for TG <150 mg/dL; 11.56% for 150–199 mg/dL; 18.29% for 200 mg/dL or higher). In adjusted models, TG 150–199 mg/dL and TG 200 mg/dL or higher were strongly associated with ApoB 130 mg/dL or higher (OR 4.25 and 7.16, respectively; both p<0.001) and with discordance (OR 11.88 and 25.70; both p<0.001). Statin use was independently associated with lower odds of ApoB 130 mg/dL or higher (OR 0.39; p<0.001). Exclusion of TG 400 mg/dL or higher did not materially alter agreement estimates. LDL-C and ApoB demonstrate differences in cardiovascular risk classification in routine laboratory practice. Although discordance was infrequent, hypertriglyceridemia strongly identified individuals with elevated ApoB and discordant classification. These findings support the selective incorporation of ApoB testing in patients with hypertriglyceridemia (TG 150 mg/dL or higher), highlighting the importance of ApoB in refining cardiovascular risk stratification, in accordance with current ACC/AHA recommendations.