Biomarker

LDL Particle Number (LDL-P)

Last updated 2026-05-30· 1 min read· Evidence: observational

Reviewed by the Ultimate Longevity Bible editorial team. Educational reference — not medical advice. See disclaimer.

Observational— Equivalent to apoB; chooses one or the other

What it measures

NMR spectroscopy counts the number of LDL particles directly (in nmol/L), and reports subclasses (small, medium, large LDL) plus VLDL and HDL subclasses. Particle count is a more accurate atherogenic-burden estimate than cholesterol-mass-only measurements.

LDL-P vs apoB

Both measure essentially the same biology — the number of atherogenic particles in plasma. ApoB is cheaper, available on standard machines, and internationally standardised. LDL-P provides additional subclass information that has clinical value in some research contexts but less in routine practice.

If both are available, they almost always agree. Pick one and follow it.

When subclass info adds value

Family-history-positive patients with normal LDL-C wanting better characterisation.
Treatment-decision uncertainty in middle-aged adults.
Tracking response to lifestyle / pharmacological treatment.

References

Cromwell, W. C. et al. LDL particle number and risk of future cardiovascular disease in the Framingham Offspring Study. J. Clin. Lipidol. 1, 583–592 (2007).