Test Quick Guide

Low-density lipoprotein particle (LDL particle or LDL-P) testing evaluates LDL-P according to their concentration in the blood. It may provide useful information for assessing your cardiac risk if you have a personal or family history of heart disease at a young age, especially if your total cholesterol and LDL cholesterol (LDL-C) levels are not significantly elevated.

About the Test

Purpose of the test

While for many people, the standard LDL-C test is a good indicator of risk of cardiovascular disease (CVD), research has found that some people with healthy levels of LDL-C (known as “bad cholesterol”) still have an increased risk of CVD.

Similarly, if you have some chronic conditions such as diabetes, you may have increased risk even though your LDL-C is at a healthy level. For these populations, it has been suggested that the number of LDL-P might be an additional factor to consider when determining your CVD risk. In these cases, LDL-P testing may be used to further evaluate your CVD risk.

What does the test measure?

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.

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 is in the blood.

Traditional lipid testing measures the amount of LDL-C present in the blood. But it does not evaluate the number of LDL-P, which 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 the risk of CVD than LDL-C. Researchers think increased LDL-P could be one of the reasons that some people have heart attacks even though their total cholesterol and LDL-C levels are not particularly high.

When should I get this test?

This testing may be ordered as part of an overall evaluation of cardiac risk when you have a personal or family history of early CVD, especially when you don’t have typical cardiac risk factors, such as high cholesterol, high LDL-C, high triglyceride, low HDL cholesterol, smoking, obesity, inactivity, diabetes, and/or hypertension.

Your health care practitioner may order LDL-P testing, along with other lipid tests, after you have made lifestyle changes and/or been treated with lipid-lowering medications to determine whether treatment is working.

Although it is not generally recommended as a screening test, a few health care providers are ordering LDL-P along with a battery of other cardiac risk tests when they are attempting to determine someone’s overall risk of developing CVD.

Finding an LDL Particle Test

How can I get an LDL particle test?

LDL-P testing is usually performed at a doctor’s office or another medical setting like a hospital or lab. These tests are normally ordered by a doctor but may be available without orders from your doctor at a walk-in lab.

Can I take the test at home?

No, the LDL-P test is not available as a self-administered home test.

How much does the test cost?

The cost of an LDL-P test will vary depending on factors such as where the test is done, and whether you have health insurance. When ordered by a doctor, insurance typically covers the test, although you may have to pay a copay or deductible. Your doctor’s office, lab, and health plan can provide information about any out-of-pocket costs that may be your responsibility.

Taking the LDL Particle Test

The LDL-P test usually requires a blood sample, which is usually taken from your arm in a doctor’s office, health clinic, hospital, or lab.

Before the test

You may need to fast for eight to 12 hours before this test; only water is permitted. Follow any instructions you are given.

During the test

A blood sample is taken from a vein in your arm. The person taking the sample may tie a band around your upper arm and will clean the area where the needle will be inserted into your skin. A small amount of blood is drawn into a tube. You may feel a slight sting when the needle enters your skin.

The process of taking a blood sample usually takes just a few minutes.

After the test

At a doctor’s office or lab, you will be asked to apply gentle pressure to the site with a bandage or a piece of gauze after the needle is withdrawn. This will help stop bleeding and may prevent bruising. Next, the site will be bandaged. You may resume your normal activities following the test.

A blood draw is a very low-risk procedure. You may have slight bruising at the site where the blood sample was taken.

LDL Particle Test Results

Receiving test results

The doctor who ordered your LDL-P test may share the results with you, or you may be able to access them through an online patient portal. LDL-P test results are usually available within a few business days.

Interpreting test results

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 among different 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 CVD above and beyond the risk associated with LDL-C.

You may want to ask your doctor the following questions:

  • How can I decrease my LDL-P?
  • What is LDL subfraction and how is it used?
  • How long may it take before I see a change in my LDL-P?


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