- The best sample is after 12 hours of fast and that is the morning sample.
- Best sample is a serum and separated within 2 hours of the collection.
- This test may be done on Serum or Plasma (EDTA) but not oxalate, citrate or fluoride.
- The serum is stable at 4 °C for 5 to 7 days and 3 months at -20 °C.
- Avoid freezing and thawing.
- The result with EDTA plasma is 3% lower than serum.
- Sample with Cholesterol above 500 mg/dL should be diluted.
- Try to separate serum or plasma from the cells within 2 hours.
- Best sample is after 12 to 14 hours of fast.
- Pregnancy may give a high level.
- Drugs that may increase the level are anabolic steroids, corticosteroids, oral contraceptives, vitamin D, phenytoin, thiazide diuretics, and cyclosporin.
- Drugs that may decrease the level are captopril, colchicine, erythromycin, isoniazid (INH), lovastatin, neomycin, bile salt binding agents, androgens, niacin, and nitrates.
Purpose of the test
- Cholesterol level is estimated to determine the coronary artery disease risk.
- This test may be needed to rule out hyperlipidemia.
- Cholesterol is absorbed in the diet and synthesized in the liver and gut. It is a precursor of steroid hormone and bile acids.
- Cholesterol is present in the diet, mostly comes from the animal source and absorbed by the GItract.
- Another source is endogenous like liver and other tissues.
- All the cells have the ability to synthesize the cholesterol and 90% occurs in the liver and intestines.
- Malnutrition will give low cholesterol formation.
- Cholesterol absorption:
- The cholesterol enters the intestine from following sources:
- Food like egg yolk, meat, fat-diary products, and seafood, the average amount is 400 to 700 mg/day.
- Plant sterols (200 to 300 mg ) are ingested daily. These are poorly absorbed.
- Bile, provide another fraction of cholesterol.
- Intestinal secretions and turn over of the intestinal mucosal cells are another source.
- Bile acids are detergents and are the most important factor affecting micelles formation.
- In the absence of bile acids, digestion and absorption of the cholesterol and triglyceride are severely affected.
- Most absorption of the cholesterol takes place in the jejunum and ileum.
- When cholesterol enters the intestinal cells then it is packaged with triglycerides, phospholipids, apolipoprotein into large lipoprotein called chylomicrons.
- When there is an increased amount of fat in diet particularly triglycerides 98%, will result in more micelles formation which in turn allows more cholesterol to be solubilized and absorbed.
- Cholesterol once formed is enter the blood circulation.
- It is then esterified and combine with apoprotein and apolipoprotein and ultimately carried as a lipoprotein.
- Biosynthesis of Cholesterol
- Cholesterol synthesis takes place in three stages.
- The starting molecule is acetate.
- All body cells have the ability to synthesize cholesterol from Acetyl Co A, but 90% it takes place in the liver.
- Cholesterol exists in two forms:
- Free cholesterol.
- Esterified cholesterol.
- 75 to 85% of the total cholesterol is in form of esterified cholesterol.
- Cholesterol can be derived from a dietary source like meat, eggs, butter, and plants.
- 30 to 60% of the dietary cholesterol is absorbed.
- Once cholesterol is absorbed into the mucosal cells then it becomes part of the large micelle is called Chylomicron.
- Cholesterol is blood lipid ( fat ).
- Cholesterol is a normal part of RBC.
- Cholesterol, when increased, leads to atherosclerosis and is the main lipid.
- Cholesterol is the basic unit of hormone produced by adrenal glands, ovaries, and testes.
- cholesterol is needed for bile acids and cellular membranes.
- Cholesterol is transported in the circulation by carrier proteins.
- Cholesterol bound to high-density lipoprotein (HDL- cholesterol) is known as good cholesterol. This will prevent atherosclerosis.
- Cholesterol bound to low-density protein (LDL-cholesterol) is known as bad cholesterol and increases the chances of atherosclerosis.
- Also the same is the cholesterol bound to very low-density lipoprotein (VLDL) is bad cholesterol.
- Increased Cholesterol level is associated with atherosclerosis and coronary vessels disease.
- The desired level to prevent coronary disease is < 200 mg/dl
- Moderate risk is 200-239 mg/dl
- High risk is > 240 mg/dl
- CSF <0.5 mg/dl
||Male mg /dL
||Female mg /dL
||44 to 103
||50 to 108
|0 to 4 years
||114 to 203
||112 to 200
|5 to 9 years
||121 to 203
||126 to 205
|10 to 14 years
||119 to 202
||124 to 201
|20 to 24 years
||124 to 218
||122 to 216
|30 to 34 years
||138 to 254
||130 to 230
|40 to 44 years
||151 to 268
||147 to 252
|50 to 54 years
||158 to 277
||162 to 285
|60 to 64 years
||159 to 276
||172 to 297
||144 to 265
||173 to 280
- To convert into SI unit x 0.0259 = mmol/L
- Desirable level is < 170 mg/dl
- Moderate risk is 170-199 mg/dl
- High risk is > 200 mg/dl
Above 240 mg/dL needs treatment.
Now a days cardiology association recommend the level to be around 160 mg/dl.
- level < 160 mg /dl very low risk
- level 160—199 mg/dl low risk
- level 200—239 mg/dl moderate risk
- level 240—279 mg/dl high risk
- level > 280 mg/dl very high risk
ATP III (Adult treatment panel) recommendations are:
- Desirable level = <200 mg/dL
- Borderline level = 200 to 239 mg/dL
- High Risk level = >240 mg/dL
Increased Cholesterol (Hypercholesterolemia):
- Familial combined hyperlipidemia.
- Hyperlipoproteinemia type, 1V, V.
- Intra- and extrahepatic cholestasis.
- Nephrotic syndrome, and chronic renal failure.
- Malignant neoplasm of pancreas and prostate.
- Diabetes mellitus.
- Glycogen storage diseases type 1 (Von Gierke disease).
- biliary cirrhosis.
Decrease Cholesterol (Hypocholesterolemia):
- alpha-Lipoprotein deficiency.
- Hepatocellular necrosis.
- Malignant neoplasm of the liver.
- Malabsorption and malnutrition.
- Severe acute illness.
- Extensive burns.
- Rheumatoid arthritis.
- Cholesterol-lowering medications.
Prevention and Interpretation:
|Total cholesterol <200 mg/dL
||Check after 5 years
|Total cholesterol 200 to 239 mg/dL
||0 to 1 risk factor and no coronary disease. Needs diet control and repeat test after one year.
|Total cholesterol >240 mg/dL
||Diet control and/or drugs intervention
Risk factors are:
- Cigarette smoking.
- Cerebrovascular disease.
- Diabetes mellitus.
- The family history of coronary heart disease.
- Sex as in male.
- Overweight >30%
- peripheral occlusive vascular disease.
- There is variation in the level of cholesterol so take at least two sample.
Possible References Used
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