- This test is done on the serum.
- Fasting sample is preferred. Advised the patient to fast for 12 to 14 hours.
- This test can be done on plasma as well.
- Can store serum or plasma at 4 °C for 4 days (can keep for 5 to 7 days).
- Don't use oxalate, fluoride, citrate or heparin for the collection of the blood.
- HDL values are age and sex-related.
- HDL value is increased in Hypothyroidism and decreased in Hyperthyroidism.
- Drugs that increase the value are oral contraceptives, aspirin, phenothiazine, steroids, and sulphonamides.
- Smoking and alcohol decrease the HDL value.
Purpose of the test
- Advised to evaluate the coronary artery disease risk.
- This can be advised as the part of a lipid profile.
- Lipoproteins are insoluble so these are transported in the plasma as a macromolecular complex.
- Lipoproteins are sphericle particle with:
- Nonpolar lipids are triglycerides and free cholesterol.
- Polar lipids are phospholipids and free cholesterol.
- Lipoprotein is classified by electrophoresis on the basis of their physical and chemical structure as follows:
- Chylomicron. (These are primarily triglycerides).
- LDL. (Beta-lipoprotein These are primarily cholesterol).
- VLDL. (Pre-beta - lipoprotein These are mainly triglycerides).
- HDL. (Alpha – lipoprotein, These are mainly protein with the small amount of cholesterol)
- The outer covering lipoproteins are called Apoprotein and these are classified into:
- Apo- B.
- Apolipoproteins are a hydrophilic component of the lipoproteins.
- While lipids like cholesterol and triglycerides are hydrophobic and need to be placed in water-soluble micellar structures (Apolipoproteins) in order to be transported in the plasma.
- In the case of endogenous pathways, the lipoproteins are synthesized in the liver from carbohydrates and fats.
- High-density lipoprotein cholesterol is produced by the liver and intestine.
- This can be separated by electrophoresis and ultracentrifugation.
- HDL composed of phospholipids and apolipoprotein (Apo A-1 and Apo - A-II), these are almost 90% of the total protein.
- The ratio of Apo - A-1 to Apo - A-11 is ∼ 3:1 by weight.
- The dominant Apoprotein is Apo-A I (67%) and it is followed by A II, C, and E.
- This may be responsible for the transport of dietary cholesterol.
- HDL plays a role in the transportation of cholesterol to the liver from the tissue where it is excreted in the bile.
- HDL transport cholesterol to the liver where cholesterol serves as the precursor of the bile acids or part of VLDL component.
- While lipoproteins transport cholesterol, triglycerides, and other insoluble fats.
- HDL (Composition) consists of:
- Cholesterol 6%
- Cholesterol ester 13%
- Triglycerides 3%
- Phospholipids 28%
- Protein 50%
- HDL has very few triglycerides.
- There is a high percentage of proteins, phospholipids, and cholesterol.
- The ratio of esterified and free cholesterol is 3:1.
- Decreased level of HDL is atherogenic.
- HDL Raised level protect against atherosclerosis by removing the cholesterol from the arteries and taking it to the liver.
- HDL and LDL may combine to maintain cellular Cholesterol balance through the mechanism of LDL moving cholesterol into the arteries and HDL removing it from the arteries.
- HDL-C is good cholesterol and is proportional to coronary artery disease (CAD) risk.
- When there is high cholesterol with a high level of HDL, the treatment is not indicated.
- Functions of HDL:
- HDL are the carriers of cholesterol from the peripheral tissue.
- From peripheral tissue, HDL carries cholesterol to liver for excretion in the bile known as reverse cholesterol transport.
- HDL has a protective role by preventing cellular uptake of cholesterol and lipids.
- HDL protects against cardiovascular diseases.
Table showing HDL and its relationship with coronary heart disease
|Risk of heart disease
||60 mg/dL HDL
||70 mg/dL HDL
||45 mg/dL HDL
||55 mg/dL HDL
||25 mg/dL HDL
||35 mg/dL HDL
- Total cholesterol / HDL-cholesterol ratio is very important to know the risk of coronary heart disease.
- A high ratio is associated with increased risk.
- The normal ratio should be at least 5:1 and the best is 3:1.
Total cholesterol / HDL-cholesterol Ratio Risk for Coronary disease
|Above average X 2 times
|Above average X 3 times
- HDL-cholesterol level of 70 mg/dl or greater is associated with longevity of life.
|| Male mg/dL
|| Female mg/dL
| Cord blood
||6 to 53
||13 to 56
| 5 to 9 year
||38 to 75
|| 36 to 73
| 10 to 14 year
||37 to 74
||37 to 70
| 15 to 19 year
||30 to 63
||35 to 74
| 20 to 24 year
||30 to 63
||33 to 79
| 25 to 29 year
|| 31 to 63
||37 to 83
|30 to 34 year
||28 to 63
||36 to 77
|35 to 39 year
||29 to 62
||34 to 82
|40 to 44 year
||27 to 67
||34 to 88
|45 to 49 year
||30 to 64
||34 to 87
|50 to 54 year
||28 to 63
||37 to 92
|55 to 59 year
||28 to 71
||37 to 91
|60 to 64 year
||30 to 74
||38 to 92
|65 to 69 year
||30 to 75
||35 to 96
||31 to 75
||33 to 92
- To convert into SI unit x 0.0259 = mmol/L
- Male = >50 mg/dL
- Female = >55 mg/dL
- Men= 36 to 65 mg/dl or > 45 mg/dl (>0.75 mmol/L).
- Women= 35 to 80 mg/dl or > 55 mg/dl (>0.91 mmol/L).
Abnormal values of HDL:
- <25 mg/dl = Coronary heart disease risk is 2 times and this is a dangerous level.
- 26 to 35 mg/dl = The risk is 1.5 times. This is a high-risk group.
- 36 to 44 mg/dl = The risk is 1.2 times. This is a moderate risk group.
- 45 to 59 mg/dl = This is average risk group.
- Above 60 mg/dl = Below average risk group.
- Critical values:
- Male = less than 35 mg/dl.
- Female = less than 40 mg/dl.
Increased HDL-C value seen in:
- A chronic liver disease like cirrhosis, hepatitis, and alcoholism.
- Long-term vigorous exercises.
- Familial hyper- alpha-lipoproteinemia.
- The increased level may be due to some drugs.
- Estrogen therapy.
- Moderate intake of alcohol.
- Insulin therapy.
Decreased HDL-C values seen in:
- Poorly controlled diabetes
- Chronic renal failure, uremia, and nephrotic syndrome.
- Familial hypo-alpha-lipoproteinemia.
- alpha and beta – lipoproteinemia.
- The decreased level may also be seen in some of the drugs.
- Antihypertensive drugs.
Table showing the summary of characteristics of the lipoproteins
||Creamy layer, slightly turbid
||Clear, or yellow-orange tint
||Turbid to opaque
|Size (diameter nm)
||4 to 10
||19.6 to 22.7
||25 to 70
||α - region
||β - region
||Pre - β region
||0.4 to 30 x 109
||3.6 x 109
||2.75 x 109
||5 to 10 x 109
|Synthesized in (Tissue of origin)
||Intestine and liver
||Liver and intestine
|Composition by weight in %
| Cholesterol esterified
||11 to 14
| Cholesterol unesterified
||5 to 8
||44 to 60
||20 to 23
||4 to 11
||Moderately to Markedly raised
|Clinical significance of
||Pancreatitis and acute abdomen
||Decreased risk of CAD
||Increased risk of CAD
||Increased risk of CAD
||Transport dietary lipids to tissue
||Carry cholesterol from tissue to liver
||Carries cholesterol to tissue
||Transport endogenous TG from liver to adipose tissue
Possible References Used
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