A blood sample drawn from a vein in your arm
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.
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.
How is the test used?
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:
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?
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?
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?
Is there any way to lower my Lp(a)?
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.)