Cholesterol

Blood total cholesterol levels have long been known to be related to coronary heart disease (CHD). In recent years, in addition to total cholesterol, high density lipoprotein cholesterol (HDL-C) has become an important tool used to assess an individual’s risk of developing CHD since a strong negative relationship between HDL-C concentration and the incidence of CHD was reported.

Thus, there has been substantial interest in HDL-C measurements, and most clinical laboratories routinely perform HDL-C analysis. Selective chemical precipitation techniques are widely used for the determination of HDL-C such as heparin-manganese, dextran sulfate-magnesium, and phosphotungstate-magnesium. However, these techniques require physical separation via centrifugation, which is not suited to large scale lab use. The Trinity Biotech EZ HDL Cholesterol test eliminates the precipitation procedure by employing a specific antibody, and thus, can be applied on automated analyzers.


Principle:

Anti-human ß-lipoprotein antibody in Reagent 1 binds to lipoproteins (LDL, VLDL, and chylomicrons) other than HDL. The antigen-antibody complexes formed block enzyme reactions when Reagent 2 is added. Cholesterol esterase (CHE) and cholesterol oxidase (CO) in Reagent 2 react only with HDL-C. Hydrogen peroxide produced by the enzyme reactions with HDL-C yields a blue color complex upon oxidase condensation with FDAOS [N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3,5-dimethoxy-4 fluoro-analine, sodium salt] and 4-aminoantipyrine (4AA) in the presence of peroxidase (POD). By measuring the absorbance of the blue color complex produced, at approximately 600 nm, the HDL-C concentration in the sample can be calculated when compared with the absorbance of the EZ HDL Calibrator.


Diagnostics Implications:

About one-fourth to one-third of blood cholesterol is carried by high-density lipoprotein (HDL). HDL cholesterol is known as ‘good’ cholesterol, becasue high levels of HDL seem to protect against heart attack. Low levels of HDL (less than 40 mg/dL) also increase the risk of heart disease. Medical experts think that HDL tends to carry cholesterol away from the arteries and back to the liver, where it is passed from the body. Some experts believe that HDL removes excess cholesterol from arterial plaque, thus slowing it’s build up.

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