Apolipoproline A-1 (apo A-I) is a protein that has a specific role in the metabolism of lipids and is the main protein component in high-density lipoprotein (HDL, the “good cholesterol”). This test measures the amount of apo A-I in the blood. Apolipoproline A-1 combine with lipids to transport them throughout the bloodstream. Apolipoproline A-1 provide structural integrity to lipoproteins and shield the water-repellent (hydrophobic) lipids at their center. Most lipoproteins are cholesterol- or triglyceride-rich and carry lipids throughout the body for uptake by cells. HDL, however, is like an empty taxi. It 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. HDL’s reverse transport 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, deposits resulting from atherosclerosis that can lead to cardiovascular disease (CVD). Apolipoproline A-1 A is the taxi driver. It 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. Deficiencies in apo A-I correlate with an increased risk of developing CVD.
How is the sample collected for Apolipoproline A-1 testing?
A blood sample is obtained by inserting a needle into a vein in the arm. As an alternative, particularly in pediatric care, the blood sample is obtained by pricking the heel or fingertip.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed; however, since this test may be performed at the same time as a complete lipid profile, fasting for at least 12 hours may be required.