Lipoprotein (a)

This is a test used to give your caregiver additional information about your risk of developing heart disease. It is used when you have a family history of elevated Lp(a) levels and/or a family history of premature CAD. It is also used when you have heart disease but your lipid profile is normal or shows only mildly elevated levels of cholesterol and/or low-density lipoprotein (LDL).

Lp(a) is an independent risk factor for heart disease. It is a lipoprotein, an LDL molecule with another protein (Apolipoprotein (a)) attached to it. In the body, Apolipoprotein (a) can interfere with the function of plasminogen. This can result in blood clot formation. Apolipoprotein (a) can also help bind LDL molecules to artery walls. This speeds up plaque formation and the narrowing and hardening of the arteries.

The Lp(a) molecule consists of a lipid-rich core surrounded by an Apolipoprotein B-100 (Apo B-100) molecule and an Apolipoprotein (a) molecule. The size of the Lp(a) molecule is consistent for one person but it varies across the human population. Lp(a) size varies because its Apolipoprotein (a) has a genetically varying number of units (called kringles) in it. As the number of kringles rises, so does the size of the Lp(a) molecule.

Lp(a) levels will remain fairly constant in an individual over a lifetime. They are slightly lower in men and they will rise a bit higher in post menopausal women. Lp(a) levels also vary by ethnicity. Those of African American descent tend to have levels 3 to 4 times higher than Caucasians. However, for reasons that are not well understood yet, they do not have a higher risk for CAD. This may be because the size of the molecule does not correlate with levels in African Americans. In people of European ancestry, larger forms of Lp(a) are associated with lower blood levels, while smaller forms are associated with higher levels.

PREPARATION FOR TEST

A blood sample is obtained by inserting a needle into a vein in the arm.

NORMAL FINDINGS

  • Caucasian (5th to 95th percentile)

  • Male: 2.2-49.4 mg/dL

  • Female: 2.1-57.3 mg/dL

  • African-American (5th to 95th percentile)

  • Male: 4.6-71.8 mg/dL

  • Female: 4.4-75 mg/dL

Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your doctor after having lab work or other tests done to discuss the meaning of your test results and whether your values are considered within normal limits.

MEANING OF TEST

Your caregiver will go over the test results with you and discuss the importance and meaning of your results, as well as treatment options and the need for additional tests if necessary.

OBTAINING THE TEST RESULTS

It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.