Total Cholesterol

Lipids are fatty substances made up of cholesterol, cholesterol esters, triglycerides, nonesterized fatty acids and phospholipids. Majority of endogenous cholesterol is produced by the liver. Exogenous dietary sources include animal fats and oils. A diet high in fat, especially saturated fat, tends to raise blood cholesterol levels. High cholesterol levels in the blood encourage deposition of fat substances on blood vessel walls with potential risk for atherosclerosis especially atherosclerotic coronary artery disease. Total serum cholesterol comprises all of the cholesterol found in various lipoproteins.

Use of Test: Evaluation of lipid status especially as a risk factor for coronary artery disease. It should be performed with HDL and triglyceride tests to assess atherosclerotic risk factors.

High-Density Lipoprotein Cholesterol (HDL)

Cholesterol and its esters, triglycerides and phospholipids are all transported in the bloodstream attached to protein particles. These lipid-protein complexes are known as lipoproteins. HDL or “good cholesterol” protect against atherosclerosis by removing cholesterol and excess fat from blood vessel walls and transport them to the liver where they are removed from the body.

Use of Test: Assessment of risk for atherosclerosis, especially coronary artery disease. Investigation of lipid status in suspected hyperlipidaemia.

Low-Density Lipoprotein Cholesterol (LDL)

Most serum cholesterol is present in the LDL. LDL or “bad cholesterol” transports fat and cholesterol to various parts of the body including the blood vessels. They are closely associated with increased incidence of athero-sclerosis and coronary heart disease. LDL cholesterol levels are calculated from fasting values of total cholesterol, HDL cholesterol and triglycerides.

Use of Test: Assessment of risk for atherosclerosis, especially coronary artery disease. Investigation of lipid status in suspected hyperlipidaemia.

Cholesterol Ratio

The cholesterol/HDL ratio gives more information than does either value alone. The higher the ratio, the higher the risk for developing atherosclerosis.

Use of Test: Assessment of risk for atherosclerosis, especially coronary artery disease.

Triglycerides

Triglycerides form the main lipid component of the diet. Exogenous triglycerides are transported to the systemic circulation via the thoracic duct. The liver is the major site of endogenous triglyceride synthesis, from fatty acids and glycerol. Triglycerides comprise 95% of fat stored in tissues. Storage triglycerides can be broken down to provide energy for the body.

Use of Test: Evaluation of lipid status.