Description: Apo A1 and B is a blood test that measures that amount of Apolipoprotein A1 and Apolipoprotein B in the blood’s serum along with the ratio between B/A1. This test is used to assess cardiovascular risk. Low levels of APO A1 are associated with Coronary Artery Disease (CAD) and are said to predict CAD better then triglycerides and HDL does.
Also Known As: Apo A1 and B Test, Apo A1 Test, Apo B Test, APOAB Test, Apolipoprotein B-100 Test, Apolipoprotein Evaluation Test
Collection Method: Blood Draw
Specimen Type: Serum
Test Preparation: Fasting for 12 hours is required.
When are Apolipoprotein A1 and B tests ordered?
Apolipoprotein A-I and B, as well as other lipid tests, may be ordered as part of a screening to identify a person's risk of cardiovascular disease.
Apo A-I is a protein that plays a key function in lipid metabolism and is the most abundant protein in HDL, or "good cholesterol." Excess cholesterol in cells is removed by HDL, which transports it to the liver for recycling or elimination. Apo A-I levels tend to rise and fall with HDL levels, and apo A-I deficits are linked to an increased risk of CVD.
Apo B is a protein that plays a role in lipid metabolism and is the major protein component of lipoproteins including VLDL and LDL, popularly known as "bad cholesterol." Apo B concentrations are similar to LDL-C concentrations.
What does Apolipoprotein A1 and B blood tests check for?
Lipids are transported throughout the bloodstream by apolipoproteins, which mix with them. Lipoproteins are held together by apolipoproteins, which protect the water-repellent lipids at their core.
Lipoproteins are cholesterol or triglyceride-rich proteins that transport lipids throughout the body for cell absorption. HDL, on the other hand, is like an empty cab or taxi. It travels to the tissues to collect excess cholesterol before returning it to the liver. Cholesterol is either recycled for future use or eliminated in bile in the liver. The only mechanism for cells to get rid of excess cholesterol is by HDL reverse transport. It protects the arteries and, if enough HDL is present, it can even reverse the formation of fatty plaques, which are deposits caused by atherosclerosis and can contribute to cardiovascular disease.
Sticking with the taxi analogy, the driver is Apolipoprotein A. It permits HDL to be detected and bound by receptors in the liver at the end of the transport by activating the enzymes that load cholesterol from the tissues into HDL. Apolipoprotein A is divided into two types: apo A-I and apo A-II. Apo A-I has a higher prevalence than apo A-II. Apo A-I concentrations can be evaluated directly, and they tend to rise and fall in tandem with HDL levels. Deficiencies in apo A-I are linked to an increased risk of cardiovascular disease.
Chylomicrons are lipoprotein particles that transport dietary fats from the digestive system to tissue, primarily the liver, via the bloodstream. These dietary lipids are repackaged in the liver and combined with apo B-100 to create triglyceride-rich VLDL. This combo is similar to a taxi with a full load of passengers and apo B-100 as the driver. The taxi moves from place to place in the bloodstream, releasing one passenger at a time.
Triglycerides are removed from VLDL by an enzyme called lipoprotein lipase, which produces intermediate density lipoproteins first, then LDL. VLDL contains one molecule of apo B-100, which is kept as VLDL loses triglycerides and shrinks to become the cholesterol-rich LDL. Apo B-100 is detected by receptors on the surface of many different types of cells in the body. The absorption of cholesterol into cells is aided by these receptors.
LDL and apo B-100 transport cholesterol that is essential for cell membrane integrity, sex hormone generation, and steroid production. Excess LDL, on the other hand, can cause fatty deposits in artery walls, as well as blood vessel hardening and scarring. Atherosclerosis is a condition in which fatty deposits restrict blood arteries. The risk of a heart attack increases as the atherosclerotic process progresses.
LDL-C levels, which are typically ordered as part of a lipid profile, tend to mimic Apo B-100 levels. Many experts believe that apo B levels will eventually show to be a more accurate predictor of CVD risk than LDL-C. Others disagree, believing that vitamin B is only a modestly superior choice and that it should not be used on a regular basis. The clinical utility of apo B, as well as other developing cardiac risk markers including apo A-I, Lp(a), and hs-CRP, is still unknown.
Lab tests often ordered with Apolipoprotein A1 and B tests:
- Cholesterol Total
- HDL Cholesterol
- LDL Cholesterol
- Lipid Panel
- Lipoprotein (a)
- Lipoprotein Fractionation, Ion Mobility
Conditions where Apolipoprotein A1 and B tests are recommended:
- Cardiovascular Disease
- Heart Attack
- Congestive Heart Failure
How does my health care provider use Apolipoprotein A1 and B tests?
An apo B/apo A-I ratio can be determined by ordering both an apo A-I and an apo B test. To assess the risk of developing CVD, this ratio is sometimes used instead of the total cholesterol/HDL ratio.
An apo A-I test may be ordered in the following situations:
Assist in the diagnosis of apo A-I deficiency caused by genetic or acquired diseases.
Assist those with a personal or family history of heart disease, high cholesterol, or triglycerides in their blood.
Keep track of how well lifestyle changes and lipid therapies are working.
An apo A-I test can be ordered in conjunction with an apo B test to determine the apo B/apo A-I ratio. This ratio is occasionally used instead of the total cholesterol/HDL ratio to assess the risk of developing CVD.
As an alternative to non-HDL-C, Apo B levels may be ordered to assess the success of lipid treatment.
An apo B test may be conducted in rare circumstances to assist determine a genetic issue that causes apo B overproduction or underproduction.
What do my Apolipoprotein A1 and B test results mean?
Low apo A-I levels are linked to low HDL levels and slowed elimination of excess cholesterol from the body. Low levels of apo A-I, as well as high levels of apo B, are linked to a higher risk of cardiovascular disease.
Deficiencies in apo A-I are caused by a number of hereditary diseases. Abnormal lipid levels, notably excessive amounts of low-density lipoprotein, are common in people with certain illnesses. They frequently have a higher rate of atherosclerosis. Low apo A-I levels are caused by several genetic diseases.
Raised apo B levels are linked to elevated LDL-C and non-HDL-C levels, and are linked to an increased risk of cardiovascular disease. Elevations may be caused by a high-fat diet and/or a reduction in LDL clearance from the blood.
A direct cause of abnormal apo B levels is some hereditary diseases. Familial combined hyperlipidemia, for example, is an inherited condition that causes excessive cholesterol and triglyceride levels in the blood. Apolipoprotein B deficiency, also known as Bassen-Kornzweig syndrome, is a relatively rare hereditary disorder that results in unusually low amounts of apo B.
A variety of underlying diseases and other factors might result in abnormal apo B levels.
We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.