Comparison of methods for measurement of apolipoprotein B and cholesterol in low-density lipoproteins.

We describe a new method for the direct measurement of LDL-apolipoprotein (apo) B by using a commercial kit that isolates LDL by immunoseparation. We evaluated immunoseparation of LDL for apo B and cholesterol measurement in 46 dyslipidemic patients with LDL-cholesterol (LDL-C) between 1.5 and 8.2 mmol/L, 11 of whom had plasma triglyceride (TG) concentrations >4.0 mmol/L. There was a reasonable correlation (r = 0.94, n = 40) between LDL-apo B obtained after immunoseparation and d >1.006 kg/L apo B obtained after ultracentrifugation. LDL-C by the immunoseparation method also correlated well (r = 0.98, n = 46) with the d >1.006 kg/L cholesterol after ultracentrifugation. These results show that immunoseparation can be used to determine LDL-apo B, even in hypertriglyceridemic samples. This method may provide a quick and simple alternative for the identification of hyperapobetalipoproteinemia, even when TG concentrations are high.