Measurement of blood lipids and lipoproteins
- Robert S Rosenson, MD
Robert S Rosenson, MD
- Professor of Medicine
- Mount Sinai School of Medicine
- Director, Cardiometabolic Disorders
- Mount Sinai Heart
Lipids, such as cholesterol and triglyceride, are insoluble in plasma. They are made soluble by attachment to circulating lipoproteins that transport lipids to various tissues for energy utilization, lipid deposition, steroid hormone production, and bile acid formation. The lipoprotein consists of esterified and unesterified cholesterol, triglycerides, and phospholipids, and protein.
There are five major lipoproteins in blood: chylomicrons; very low density lipoprotein (VLDL); intermediate density lipoprotein; low density lipoprotein (LDL); and high density lipoprotein. Each of these classes of lipoproteins carries cholesterol and triglyceride to a varying degree, with LDL carrying the majority of cholesterol, and VLDL carrying the majority of triglyceride.
In general, patient care issues related to screening, diagnosis, and treatment are based on the results of the measurement of serum lipids, which is generally accomplished by obtaining a lipid profile. On occasion, measurement of serum lipoproteins is necessary for one or more of these purposes. This topic will discuss the issues relevant to the measurement of serum lipids and lipoproteins. Other issues related to lipids and lipoproteins, such as their role in atherosclerosis, are discussed separately. (See "Lipoprotein classification, metabolism, and role in atherosclerosis".)
LIPID PROFILE AND COMPONENTS
A standard serum lipid profile measures the concentration of total and HDL-cholesterol (HDL-C) as well as the triglycerides. With these values, the LDL cholesterol (LDL-C) concentration can be estimated. (See 'LDL-cholesterol' below.)
Total and HDL-C — Serum total and HDL-C are measured directly and can be obtained in fasting or nonfasting individuals; there are only small, clinically insignificant differences in these values between measurements in the fasting or non-fasting state . (See 'Fasting versus non-fasting tests' below.)
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- LIPID PROFILE AND COMPONENTS
- Total and HDL-C
- Total cholesterol to HDL cholesterol ratio
- - Friedewald equation
- - Direct measurement
- - Other indirect methods
- Causes of inaccurate results
- - After an ACS
- LDL PARTICLE SIZE AND NUMBER
- NON-HDL CHOLESTEROL
- INDICATIONS FOR MEASUREMENT
- Lipid profile
- Other measurements of LDL
- FASTING VERSUS NON-FASTING TESTS
- SOCIETY GUIDELINE LINKS
- SUMMARY AND RECOMMENDATIONS