The measurement of apolipoprotein B is used to assess the risk of developing atherosclerotic cardiovascular disease and in the diagnosis of abetalipoproteinemia or hypobetalipoproteinemia.
Lipoproteins are important carriers of cholesterol. High-density lipoprotein (HDL or "good cholesterol") takes cholesterol from the tissues and transports it back to the liver either for recycling or for biliary excretion. Since HDL works to rid the body of excess cholesterol, it is preferable that HDL levels be high. Low-density lipoprotein (LDL or "bad cholesterol") also carries excess cholesterol, but it tends to carry it to the arteries and can lead to the development of atherosclerosis. Thus, it is best to have low LDL levels to reduce the risk of developing atherosclerotic disease.
Apolipoproteins (Apo) are the protein components of lipoproteins. Two of the apolipoproteins, Apo A and Apo B, serve particularly important cholesterol control functions in the body. Apo A activates the enzymes that cause cholesterol to move from tissues to HDL and also helps to recognize HDL from receptors in the liver where cholesterol is deposited. There are two subcategories of Apo A: Apo A1 and Apo A2. The Apo A1 is the most abundant of the two and can be readily measured. Apo A1 tends to correlate with HDL levels and is believed to be preferable to HDL as an indicator of coronary artery disease (CAD) risk. There are also two types of Apo B: Apo B-100 and Apo B-48. Apo B-48 is part of the structure of chylomicrons, the major lipoproteins that initially transport lipids to the liver. From there, the lipids combine with Apo B-100 to form the very-low-density lipoproteins (VLDL) that eventually become LDL. Apo B-100 levels are correlated with LDL levels and can be measured directly. Apo B-100 is considered a risk indicator for coronary artery disease.
Apart from measuring Apo A1 and Apo B-100 separately, the evaluation of apolipoproteins also includes the calculation of the Apo B / Apo A ratio. The higher the ratio, the greater the risk of coronary heart disease. In addition to assessing the risk for coronary heart disease, these tests may also be used to monitor the patient's response to treatment for hyperlipidemia.
What Do Pathological Values Mean?
- Increase: Biliary obstruction, smoking, Cushing's syndrome, diabetes mellitus, dialysis, liver disease, hyperlipoproteinemias (types II, III, V), hypothyroidism, increased risk of coronary artery disease, nephrotic syndrome, porphyria, pregnancy, renal failure. Medications: beta-blockers, corticosteroids, cyclosporin, diuretics.
- Decrease: Chronic anemia, chronic lung disease, hyperlipidemia (type I), hyperthyroidism, inflammation, malnutrition, Reye's syndrome, Tangier disease, weight loss. Medications: cholesterol-lowering agents, estrogens, indapamide.
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. The correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings, and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.