Low-density lipoprotein (LDL cholesterol, LDL-C) is one type of lipoprotein that carries cholesterol in the blood. LDL-C consists mostly of cholesterol and similar substances with a small amount of protein. Most often, this test involves using a formula to calculate the amount of LDL-C in blood based on results of a lipid profile. Occasionally, LDL-C is measured directly.
Why Get Tested :
- Advised to evaluate the coronary artery disease risk.
- This can be advised as the part of a lipid profile.
When to get tested :
- Screening: as part of a regular health exam with a lipid profile.
- when no risk factors for heart disease are present.
- once every four to six years in adults.
- children should have a lipid profile screening at least once between the ages of 9 and 11 and then again between the ages of 17 and 21.
- 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).
- Adult = <130 mg/dL
- Children = <110 mg/dL
Calculation of LDL
The LDL can be calculated by the following formula:
- LDL = Total cholesterol – ([triglycerides ÷ 5] – HDL)
- LDL = Total cholesterol – VLDL- HDL)
- LDL = Total cholesterol — (HDL cholesterol + 1/5 x Triglycerides)
NOTE: These formulas only help if the fasting triglycerides value is < 400 mg/ dl.
Increased LDL values are seen in:
- Familial hyperlipidemia type 2.
- Familial hypercholesterolemia.
- Glycogen storage diseases.
- Secondary causes are :
- Nephrotic syndrome.
- Multiple myelomas.
- Liver disease with obstruction.
- Diabetes mellitus.
- Chronic renal failure.
- Diet high in cholesterol and saturated fats.
- Alcohol intake.
Decreased values seen in:
- Hyperlipoproteinemia type 1.
- Chronic anemias.
- Hepatocellular diseases.
- Chronic pulmonary disease.
- Reye’s syndrome.
- Acute stress like a burn.
- Inflammatory joint disease.
Table showing the summary of characteristics of the lipoproteins
|PLasma appearance||Creamy layer, slightly turbid||Clear||Clear, or yellow-orange tint||Turbid to opaque|
|Size (diameter nm)||>70.0||4 to 10||19.6 to 22.7||25 to 70|
|Electrophoretic mobility||Origin||α – region||β – region||Pre – β region|
|Molecular weight||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||Intestine and liver||Intravascular||Liver and intestine|
|Composition by weight in %|
|Cholesterol esterified||5||38||49||11 to 14|
|Cholesterol unesterified||2||10||13||5 to 8|
|Triglycerides||84||9||11||44 to 60|
|Phospholipids||7||22||27||20 to 23|
|Proteins||2||21||23||4 to 11|
|Triglycerides||Markedly raised||Normal||Normal/ Raised||Moderately to Markedly raised|
|Clinical significance of||Pancreatitis and acute abdomen||Decreased risk of CAD||Increased risk of CAD||Increased risk of CAD|
|Functions||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