LAUSR

BACKGROUND Apolipoprotein B-100 (ApoB) is a well-researched lipoprotein marker used in assessing the risk of coronary heart disease (CHD) development. Despite its continued use at the bedside, ApoB methodologies have not been thoroughly compared and may differentially discriminate CHD risk, resulting in patient misclassification. OBJECTIVE This study compared 3 ApoB immunoassays and their associations with incident CHD risk over a 12-year follow-up period in the Multi-Ethnic Study of Atherosclerosis. METHODS Plasma ApoB concentrations were measured in 4679 participants of Multi-Ethnic Study of Atherosclerosis at baseline, using 3 immunoturbidimetric methods. Roche and Kamiya reagent-based methods were analyzed on a Roche modular P analyzer, and the Diazyme reagent-based method was analyzed on a Siemens Dimension analyzer. Cox proportional analysis estimated ApoB-related risk of incident CHD over a median follow-up period of 12.5 years with adjustments for nonlipid CHD risk factors. ApoB concentrations were examined as continuous variables but were also dichotomized based on clinical designations of borderline (100 mg/dL), high (120 mg/dL), and very high ApoB levels (140 mg/dL). RESULTS Moderate to strong correlations among ApoB methods were observed (r = 0.79-0.98). ApoB concentrations (per standard deviation) were similarly associated with CHD risk and hazard ratio (95% confidence interval): Roche: 1.16 (1.03-1.30); Kamiya: 1.14 (1.02-1.28); and Diazyme: 1.14 (1.02-1.28). CONCLUSION Although all 3 ApoB were similarly associated with risk of incident CHD over the study period regardless of the reagent type, the bias between methods suggests that these reagents are not fungible, and assay harmonization may be warranted.