Total cholesterol

TOTAL CHOLESTEROL

It is generally agreed that the normal range for total cholesterol is rather wide. Serum total cholesterol is slightly higher in men than in women. It is a little lower in persons under 20 years but rises with age. It
does not appear to be much altered following meals (unlike triglyceride).
In pregnancy there is an increase which may reach 20% above normal at the 30th week.

lipid profile

The lipid profile is used as an index of its possible effect in precipitating atherosclerosis. The following table is usually used for its interpretation:
Serum total cholesterol < 5 mmol/L (<200 mg%)
HDL-Cholesterol Low risk >1.4mmol/L (>55 mg%)
High risk <0.9 mmol/L (<35 mg%)
LDL-Cholesterol Low risk <3.4 mmol/L (<130 mg%)
High risk >4.1 mmol/L (>160 mg%)
VLDL-Cholesterol Low risk <.45 mmol/L (<37 mg%)
Atherogenic index Low risk < 5 mmol/L (>6 High risk)
Serum Phospholipids 57 – 89 mmol/L (175 – 275 mg%)

Hypercholesterolaemia

Increases are found most characteristically in the primary hypercholesterolaemia (particularly types II, III and IV), nephrotic
syndrome, hypothyroidism, obstructive jaundice, primary biliary cirrhosis
and diabetes mellitus.


Raised serum cholesterol signifies hypercholesterolaemia which is considered to be a cardiovascular risk factor that may predispose to coronary thrombosis appearing as angina pectoris or myocardial infarction.

Hypocholesterolaemia

Decreases are not so well defined. Conditions that may create
hypocholesterolaemia include hyperthyroidism, malabsorption syndrome malnutrition and pernicious anaemia. Very low values occur in a beta lipoproteinaemia. Therapeutic reduction of serum cholesterol is seen during administration of lipid lowering drugs such as clofibrate, cholestyramine and nicotinic acid.

Measurement of Serum Cholesterol

Principle
Serum cholesterol is measured by the following enzymatic
reactions;
Cholesterol esters+ H2O Cholesterol esterase Cholesterol+ Fatty acids
Cholesterol+O2 Cholesterol Oxidase 4-Cholesten-3-One+H2O2
2H2O2+4-aminoantipyrine Peroxidase Red quinine + 4 H2O
By measuring the absorbency of the red quinine at 500 nm and
comparing with standard solution of cholesterol treated in the
same way and applying lamberts and Beers low , the
concentration of the test can be found.