Electrophoretic measurement of lipoprotein(a) cholesterol in plasma with and without ultracentrifugation: comparison with an immunoturbidimetric lipoprotein(a) method

Objectives: Elevated plasma lipoprotein(a) [Lp(a)] is a significant risk factor for vascular disease. Standardization of Lp(a) mass measurement is complicated by the heterogeneity of apolipoprotein(a) [apo(a)]. We investigated whether Lp(a) cholesterol measurement, which is not influenced by apo(a) size, is a viable alternative to measuring Lp(a) mass. Design and methods: Plasma Lp(a) cholesterol was measured electrophoretically, with and without ultracentrifugation, and results were compared to each other and to immunoturbidimetrically measured Lp(a) mass in 470 subjects. Results: Ultracentrifuged and whole plasma Lp(a) cholesterol levels demonstrated high correlation (R = 0.964). All samples with detectable (greater than or equal to2.0 mg/dl) Lp(a) cholesterol had Lp(a) mass > 30 mg/dl (the clinically relevant cutpoint), while 59 samples with Lp(a) mass > 30 mg/dl did not have detectable Lp(a) cholesterol. Conclusions: Lp(a) cholesterol can be measured in whole plasma without interference from VLDL lipoproteins. The relative clinical merits of measuring Lp(a) cholesterol vs. Lp(a) mass or both in combination deserves investigation. (C) 2004 The Canadian Society of Clinical Chemists. All rights reserved.