Mean lipoprotein particle size reflects the average size of lipoprotein particles (LDL, HDL, VLDL) circulating in the blood. Larger average particle size is generally associated with lower cardiovascular risk; smaller average size indicates a shift toward the atherogenic small dense pattern.

This measure is most clinically meaningful for LDL particle size, where smaller particles are more atherogenic. It can identify individuals with hidden cardiovascular risk whose standard lipid panels appear normal but whose particle pattern is unfavourable.