Apo A, Apolipoprotein A-I

This is a test to determine whether or not you have adequate levels of Apo A-I and to help determine your risk of developing coronary artery disease (CAD).

  • Apolipoproteins are the protein component of lipoproteins - complexes that transport lipids throughout the bloodstream. Apolipoproteins provide structural integrity to lipoproteins and shield the hydrophobic (water-repellent) lipids at their center.

  • Lipoproteins contain cholesterol or triglycerides and carry lipids throughout the body for uptake by cells. High-density lipoprotein (HDL the "good" cholesterol), goes out to the tissues and picks up excess cholesterol, then transports it back to the liver. In the liver, the cholesterol is either recycled for future use or excreted into bile. This is the only way that cells can get rid of excess cholesterol. It helps protect the arteries and if there is enough HDL present, it can even reverse the build up of fatty plaques in the arteries (deposits that lead to atherosclerosis and coronary artery disease).

  • Apolipoprotein A activates the enzymes that load cholesterol from the tissues into HDL and allows HDL to be recognized and bound by receptors in the liver at the end of the transport. There are two forms of apolipoprotein A, Apo A-I and Apo A-II. Apo A-I is found in greater proportion than Apo A-II (about 3 to 1). The concentration of Apo A-I can be measured directly and tends to rise and fall with HDL levels. This has led some experts to think that Apo A-I may be a better indicator of atherogenic risk than the HDL test.

  • Deficiencies in Apo A-I appear to correlate well with an increased risk of developing coronary artery disease (CAD) and peripheral vascular disease. Regular exercise is one of the best ways to raise HDL and Apo A-I. By decreasing the fat in your diet, maintaining a healthy weight, and exercising you can help decrease your risk of developing heart disease.

PREPARATION FOR TEST

Typically, a blood sample is obtained by inserting a needle into a vein in your arm. In pediatric care, the blood sample may be drawn from the fingertip.

NORMAL FINDINGS

Apo A-1

  • Adult / older adult

  • Male: 75-160 mg/dL

  • Female: 80-175 mg/dL

  • Child, 6 months to 4 years

  • Male: 67-167 mg/dL

  • Female: 60-148 mg/dL

  • Newborn

  • Male: 41-93 mg/dL

  • Female: 38-106 mg/dL

APO B

  • Adult / older adult

  • Male: 50-125 mg/dL

  • Female: 45-120 mg/dL

  • Newborn: 11-31 mg / dL

  • Child, 6 months to 3 years: 23-75 mg / dL

  • Child / adolescent, 5 to 17 years

  • Male: 47-75 mg / dL

  • Female: 45-132 mg / dL

APO A-l/APO B ratio

  • Male: 0.85-2.24

  • Female: 0.76-3.23

Lipoprotein (a)

  • Caucasian (5th to 95th percentile)

  • Male: 2.2-4.9 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.