LDL Particle Number

LDL-P (the LDL Particle Number) is the direct measure of low density lipoprotein particles. 

The causal link between high levels of LDL-P and development of cardiovascular disease (CVD) is well established.

LDL-P (LDL particle number) measures the actual number of LDL particles (particle concentration, nmol/L). It appears that LDL-P may be a stronger predictor of cardiovascular events than LDL-C.

Lipoproteins are particles that transport fats throughout the body. These particles are essential and carry a combination of proteins, vitamins, cholesterol, triglyceride, and phospholipid molecules. The composition of a lipoprotein particle changes as it circulates in the blood. Some molecules are removed and others are added, resulting in lipoprotein particles with variable amounts of cholesterol.

Low-density lipoprotein particles (LDL-P) are bi-products of fat transport that remain in circulation for an extended time. While in circulation, LDL-P can penetrate the artery wall and get stuck, forming a fatty plaque. These plaques can build over time and lead to blockages, resulting in heart attacks and strokes. The likelihood of an LDL-P getting trapped in the artery wall increases when more LDL-P are in the blood.

Traditional lipid testing measures the amount of LDL cholesterol (LDL-C) present in the blood, but it does not evaluate the number of LDL particles (LDL-P). LDL-P is often used to get a more accurate measure of LDL due to the variability of cholesterol content within a given LDL. Studies have shown that LDL-P more accurately predicts risk of cardiovascular disease than LDL-C. Researchers think that increased LDL-P could be one of the reasons that some people have heart attacks even though their total cholesterol and LDL cholesterol levels are not particularly high.

LDL-P test results are typically reported according to the testing method the laboratory uses. The report will usually include results for your total cholesterol, LDL-C and LDL-P. Additional values might include very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), LDL-C and/or HDL cholesterol, particle and size. Since different lab methods separate the subclasses based on different physical properties (particle number, size, density, and/or electrical charge), results cannot be directly compared between methods or laboratories.

In general, the result is interpreted within the framework of a lipid profile and its associated risk. If you have an increased LDL-P, this finding will add to your risk of developing cardiovascular disease above and beyond the risk associated with LDL cholesterol.