Lipoprotein (a)

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  • Also Known As:
  • Lipoprotein little a
  • Lp(a)
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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.

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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.

 

Common Questions

How is the test used?

The lipoprotein (a) or Lp(a) test is not routinely ordered. It may be used as part of a cardiac risk assessment to identify an elevated level of lipoprotein (a). The test may be used with a routine lipid panel to provide additional information about your risk for heart disease.

When is it ordered?

Lipoprotein (a) may be ordered, along with other lipid tests, when you have a strong family history of heart disease at a young age that is not explained by high LDL cholesterol or low HDL cholesterol.

Some healthcare practitioners may also order these tests when:

  • You have existing heart or vascular disease, especially when you have healthy lipid levels or ones that are only mildly elevated
  • You may have an inherited predisposition for a high cholesterol level
  • You have had a stroke or heart attack but have normal or only mildly elevated lipids

What does the test result mean?

A high Lp(a) level may increase your risk for heart disease and stroke. High Lp(a) can occur in people with a normal lipid panel. An elevated level of Lp(a) is thought to contribute to risk of heart disease independent of other lipids.

The level of Lp(a) is determined by your genes and is not easily modified by lifestyle changes or medication, such as statins. However, some non-genetic conditions may also lead to elevated Lp(a). These include low estrogen levels, severe underactive thyroid (hypothyroidism), uncontrolled diabetes, chronic kidney disease and nephrotic syndrome.

There are no known problems associated with low Lp(a). Many individuals have no detectable Lp(a) in their blood.

Is there anything else I should know?

In rare cases, an Lp(a) level may be ordered when a woman has entered menopause to see if elevations in Lp(a), tied to decreasing estrogen levels, have significantly increased her risk of developing CVD.

Should everyone have an Lp(a) test done?

Lp(a) is not a routinely ordered test. Guidelines from the American College of Cardiology and the American Heart Association state that elevated levels of Lp(a) are associated with an increased risk of early heart disease and are genetically determined but do not recommend widespread screening. Other guidelines recommend testing for individuals with a strong family history of early heart disease and/or high lipid levels, or those with intermediate cardiovascular risk, but do not recommend general screening.

Why would my healthcare practitioner want me to wait to test my lipids?

In general, lipids should not be measured during a fever or major infection, within four weeks of a heart attack, a stroke, or major surgery, right after excessive alcohol intake, with severely uncontrolled diabetes, when a woman is pregnant, or during rapid weight loss.

Why would my healthcare practitioner order an Lp(a) more than once?

Typically, the Lp(a) level is only tested once because it is usually fairly constant. Occasionally, your healthcare practitioner may order a second Lp(a) to confirm the initial level, especially if it was measured when you were ill, or to see if a woman’s risk has increased significantly after menopause.

Can I have an Lp(a) test done in my healthcare practitioner's office?

The Lp(a) test requires specialized equipment to perform and is usually performed in a reference laboratory. Your sample may be sent out for testing.

Is there any way to lower my Lp(a)?

Lp(a) levels are genetically determined and difficult to change. Niacin and estrogen (for postmenopausal women) have been shown to lower Lp(a) levels a small amount, but their effect appears to be short-term and it is not known if lowering Lp(a) actually lowers risk.

If Lp(a) levels don't really change over my lifetime, why would my healthcare practitioner prescribe treatment?

Experts are currently not recommending drug treatments for elevated Lp(a), but some are suggesting that people with elevated Lp(a) and additional risk factors should strive to lower their LDL – the “bad” cholesterol, which may help lower their overall risk.. Treatment to lower your LDL cholesterol may help lower your overall risk. (See the article on LDL Cholesterol for details.)

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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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