Cholesterol, Total, Serum
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Cholesterol is a steroid with a secondary hydroxyl group in the C3 position. It is synthesized in many types of tissue, but particularly in the liver and intestinal wall. Approximately 75% of cholesterol is newly synthesized and 25%originates from dietary intake. Normally, the cholesterol in the plasma or serum is 60% to 80% esterified. Approximately 50% to 75% of the plasma cholesterol is transported by low density lipoproteins (LDL) and 15% to 40% by high density lipoproteins (HDL).
Serum cholesterol is elevated in the hereditary hyperlipoproteinemias and in various other metabolic diseases. Moderate-to-markedly elevated values are also seen in cholestatic liver disease. Hypercholesterolemia reflects an increase of lipoproteins of 1 or more specific classes (eg, beta-LDL, alpha-1 HDL, alpha-2 HDL, or LP-X). Hypercholesterolemia is a risk factor for cardiovascular disease.
Low levels of cholesterol can be seen in disorders that include hyperthyroidism, malabsorption, and deficiencies of apolipoproteins.
Evaluation of cardiovascular risk
The National Cholesterol Education Program (NCEP) has set the following guidelines for total cholesterol:
Desirable: <200 mg/dL
Borderline high: 200 mg/dL to 239 mg/dL
High: > or = 240 mg/dL
Values above the normal range indicate a need for quantitative analysis of the lipoprotein profile.
Values in hyperthyroidism usually are in the lower normal range; malabsorption values may be <100 mg/dL, while beta-lipoprotein or apolipoprotein B deficiency values usually are <80 mg/dL.
See Lipids and Lipoproteins in Blood Plasma (Serum) in Special Instructions.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Patients must be fasting for at least 12 to 14 hours if a lipid screen is ordered. If total cholesterol is the only lipid test ordered, fasting is not necessary.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
The National Cholesterol Education Program (NCEP) has set the following guidelines for lipids (total cholesterol, triglycerides, high density lipoprotein [HDL], and low density lipoprotein [LDL] cholesterol) in adults ages 18 and up:
Desirable: <200 mg/dL
Borderline high: 200-239 mg/dL
High: > or =240 mg/dL
The National Cholesterol Education Program (NCEP) and National Health and Nutrition Examination Survey (NHANES) has set the following guidelines for lipids (total cholesterol, triglycerides, HDL, and LDL cholesterol) in children ages 2-17:
Desirable: <170 mg/dL
Borderline high: 170 -199 mg/dL
High: > or =200 mg/dL
Also see age and sex adjusted reference values in Total Cholesterol-Percentile Ranking in Lipids and Lipoproteins in Blood Plasma (Serum) in Special Instructions.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Tietz Textbook of Clinical Chemistry. Edited by CA Burtis, ER Ashwood. Philadelphia, WB Saunders Company, 1994
2. National Institute of Health (NIH) Publication. Second Report of the Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. 1993 September; 93:3096