Development of a rapid, quantitative method for LDL subfractionation with use of the quantimetrix lipoprint LDL system

Background: Recent evidence suggests that the presence of small, dense LDL is independently associated with increased risk of developing coronary artery disease. Current methods to subfractionate LDL are timeconsuming and/or technically demanding. Therefore, we have sought the development of a less complex LDL subfractionation procedure. Methods: LDL subfractions were separated using the Quantimetrix Lipoprint^TM LDL System. High-resolution 3% polyacrylamide gel tubes were scanned densitometrically (610 rim) with a Helena EDC system. A computerized method to identify and quantitatively score the resolved LDL subfractions was developed. Results from the Quantimetrix method were compared using 51 plasma samples with values obtained by nondenaturing gradient gel electrophoresis (NDGGE) and nuclear magnetic resonance (NMR) spectroscopy. Results: LDL subfractionation scores correlated significantly (P < 0.05) with triglyceride, HDL-cholesterol, apolipoprotein B100, and LDL-cholesterol/apolipoprotein B100 (r = 0.591, -0.392, 0.454, and -0.411, respectively). For 51 samples, the Quantimetrix method classified 21 with small, 14 with intermediate, and 16 with large LDL. Of the 21 samples classified as small by Quantimetrix, 20 (95%) were classified as small (n = 18) or intermediate (n = 2) by NDGGE. All of the 16 specimens classifled as large by Quantimetrix were either large (n = 14) or intermediate (n = 2) by NDGGE. LDL score was inversely correlated (r = -0.674; P <0.0001) with LDL particle size determined by NMR spectroscopy. Conclusions:A quantitative method for the assessment of LDL particle size phenotype was developed using the Quantimetrix Lipoprint LDL System. The method can be performed in less than 3 h in batch mode and is suitable for routine use in clinical laboratories.