AsseyMethod: Photo Colorimetric
Abbrevation: Apo A1
Sector: Biochemistry
SampleType: S
S.Vol: 0.4
Transport: at 2-8˚c, -20˚c
Storage: Immediately at 2-8 ˚ c at -20 ˚c - up to Analyse
Test Name: Apolipoprotein A
Normal Range: Female:120-190 Male:110-170
To determine whether or not you have adequate levels of apo A-I, to diagnose people with specific apo A deficiency and to help determine your risk of developing coronary heart disease (CHD)
This is a not a routinely performed test and is currently limited to hospital specialists, and specialist testing laboratories. It can be measured when you have hyperlipidaemia and/or a family history of CHD or peripheral vascular disease; when your doctor is trying to assess your risk of developing heart disease; when apo A deficiency is suspected and when you are monitoring the effectiveness of lipid treatment and/or lifestyle changes.
Usually, a blood sample taken from a vein in your arm
None; however, this test is often requested at the same time as other tests that require fasting, so you may be instructed to fast for 12 hours prior to having this test.
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 centre.
Most lipoproteins are cholesterol- or triglyceride-rich and carry lipids throughout the body, for uptake by cells. High-density lipoprotein (HDL - the "good" cholesterol), 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 in the arteries (deposits that lead to atherosclerosis and coronary artery disease).
Apolipoprotein A is the taxi driver. It activates the enzymes that load cholesterol from the tissues into HDL and allows HDL to be recognised 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, unlike HDL, 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 the risk of coronary artery disease from the build-up of atheroma than the HDL test, but this has yet to be proven definitively.
Deficiencies in apo A-I appear to correlate well with an increased risk of developing CHD and peripheral vascular disease. The routine use of apo A-I is however not currently accepted as standard care in this country.
How is the sample collected for testing?
Typically, a blood sample is obtained by inserting a needle into a vein in your arm. As an alternative, particularly in paediatric care, the blood sample is taken from the 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 lipid profile, fasting for at least 12 hours may be required.