Effect of HDL disk and LDL dimer presence on lipoprotein particle number determination and subclassification

Area of Science:

• Cardiovascular research
• Analytical chemistry
• Biochemistry

Background:

• High-density and low-density lipoproteins (HDL and LDL) are crucial biomarkers for chronic disease risk.
• Accurate measurement of lipoprotein particle concentrations (HDL-P and LDL-P) is vital for clinical diagnosis.
• Existing methods may contain biases, particularly for small HDL and LDL subclasses.

Purpose of the Study:

• To identify and quantify sources of bias in HDL-P and LDL-P measurements.
• To investigate the impact of non-spherical particle shapes (e.g., HDL disks, LDL dimers) on particle counting.
• To propose a corrected methodology for more accurate lipoprotein subclass analysis.

Main Methods:

• Plasma samples were analyzed using asymmetric-flow field-flow fractionation (AF4) coupled with LC-MS/MS.
• Lipoprotein concentration-size profiles were deconvoluted into distinct HDL and LDL subspecies.
• Molecular volume ratios were used to evaluate particle models and identify deviations from spherical geometry.
• Corrections were applied based on identified biases for small HDL disks and small LDL dimers.

Main Results:

• Evidence found for small HDL disks and small LDL dimers as sources of bias when assuming spherical geometry.
• Corrected particle sizes (k*d_m) showed improved agreement with consensus values.
• Post-correction differences between AF4-LC-MS/MS and NMR decreased significantly for both HDL-P (20% to 4.9%) and LDL-P (-47% to -5.7%).
• Correlation between methods improved substantially after applying corrections.

Conclusions:

• Standardization of lipoprotein subclass measurement methods is recommended, focusing on apoA1 and apoB.
• Harmonization of HDL and LDL subclass definitions based on composition and structure, rather than strict size cutoffs, is supported.
• The findings enhance the reliability of lipoprotein subclass analysis for clinical risk stratification.