LDL-P (LDL particle number)

LDL-P, or LDL particle number, quantifies the total concentration of low-density lipoprotein particles in plasma rather than their cholesterol payload, typically measured by nuclear magnetic resonance (NMR) spectroscopy or ion-mobility analysis. Because each LDL particle carries one apolipoprotein B-100 molecule, LDL-P is numerically equivalent to apoB from LDL; both reflect the atherogenic particle burden available for subendothelial retention. In discordance analyses — where LDL-C and LDL-P diverge, most commonly in the setting of hypertriglyceridaemia, insulin resistance, or low HDL — LDL-P is consistently the stronger predictor of cardiovascular events, supporting the concept that it is particle number rather than cholesterol mass per particle that drives atherosclerosis risk. Reference intervals are typically reported as nmol/L, with higher cardiovascular risk associated with LDL-P above approximately 1,000–1,200 nmol/L.