Also Known As
Lipoprotein little a
Lp(a)
This article was last reviewed on
This article waslast modified on April 1, 2019.
At a Glance
Why Get Tested?

To give your healthcare practitioner additional information about your risk of developing heart disease; as part of a cardiac risk assessment

When To Get Tested?

When you have a family history of heart disease at a young age; when you have heart disease or have had a heart attack or stroke but your lipid panel results are normal or show only mildly elevated cholesterol and/or low-density lipoprotein cholesterol (LDL-C)

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

Lipoprotein (a) does not require test preparation. However, Lp(a) is often performed at the same time as a lipid panel and fasting for 9-12 hours may be required for the lipid panel. In this case, only water is permitted.

What is being tested?

Lipoprotein (a) or Lp(a) is one type of lipoprotein that carries cholesterol in the blood. It consists of a low-density lipoprotein (LDL) molecule with another protein (Apolipoprotein (a)) attached to it. This test measures the Lp(a) level in the blood to help evaluate your risk of developing cardiovascular disease (CVD).

Like LDL cholesterol (the "bad" cholesterol), Lp(a) is considered a risk factor for CVD. However, Lp(a) does not respond to typical strategies to lower LDL cholesterol such as diet, exercise, or most lipid-lowering medications, such as statins. The amount of Lp(a) that you have is determined by the genes you inherited, and it remains relatively constant over your lifetime. A high level of Lp(a) is thought to contribute to your overall risk of CVD, making this test potentially useful as a cardiovascular risk marker.

The protein portion of Lp(a) consists of:

  • Apolipoprotein B (Apo B) – a protein that is involved in the breakdown (metabolism) of lipids and is the main protein constituent of lipoproteins such as LDL and very low-density lipoprotein (VLDL)
  • Apolipoprotein (a) – a second protein component, which is attached to the Apo B. Apolipoprotein (a) has an unusual structure and is thought to inhibit clots from being broken down normally. The size of the apolipoprotein(a) portion of Lp(a) varies in size from person to person and tends to be smaller in Caucasians than in those of African ancestry. The significance of the variation in size in contributing to CVD risk is complex, but there is some evidence that smaller size increases risk. Most Lp(a) tests do not measure the size of apolipoprotein (a) because they measure and report only the level of Lp(a) in blood.

Since about 50% of the people who have heart attacks have a normal cholesterol level, researchers have sought other factors that may have an influence on heart disease. It is thought that Lp(a) may be one such factor. Lp(a) has two potential ways to contribute to heart risk: 

  • Lp(a) can promote deposits of LDL cholesterol in blood vessel walls and the formation of plaque on the walls of blood vessels. Plaques can narrow or eventually block the opening of blood vessels, leading to hardening of the arteries (atherosclerosis) and increased risk of numerous health problems, including heart disease and stroke.
  • Apo(a) has a structure that can inhibit enzymes that dissolve clots, so Lp(a) may promote the formation of clots in the arteries.

For these reasons, Lp(a) may be more of a risk factor for atherosclerosis than LDL cholesterol.

Accordion Title
Common Questions

You may be able to find your test results on your laboratory's website or patient portal. However, you are currently at Lab Tests Online. You may have been directed here by your lab's website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab's website or portal, or contact your healthcare practitioner in order to obtain your test results.

Lab Tests Online is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called "normal" values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

For more information, please read the article Reference Ranges and What They Mean.

View Sources

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