Also known as: Cholesterol; total cholesterol
Name: Total cholesterol
Related tests: HDL cholesterol, LDL cholesterol , Lipid profile, Triglycerides
Why is the test done?
To assess the risk of cardiovascular disease.
When is the test done?
Total cholesterol should be tested every four years for primary prevention, and more often if other major cardiovascular risk factors are present or to monitor cholesterol-lowering treatment.
What samples are required?
A blood sample from a vein or a finger-prick.
What is being analysed?
Cholesterol is an essential steroid; as well as being a component of cell membranes, it is the precursor of steroid hormones, which are involved in many biological processes such as development, growth and reproduction. Cholesterol is also used to make bile acids, which are essential for absorbing fats and fat-soluble vitamins from the gut. Circulating cholesterol is bound to protein complexes, forming lipoproteins; there are several classes of lipoprotein with different composition and functions: LDL (low-density lipoprotein) carries cholesterol from the liver to the peripheral tissues, while HDL (high-density lipoprotein) is involved in the “reverse transport” of cholesterol, i.e. removing excess cholesterol from the peripheral tissues and taking it to the liver. The total cholesterol test measures the cholesterol contained in both HDL and LDL.
How is the sample collected for testing?
The sample is taken from a vein in the arm or by pricking a fingertip.
How is it used?
When is it requested?
What does the test result mean?
Is there anything else I should know?
How is it used?
Unlike many other tests used to diagnose or monitor a disease, cholesterol is used to estimate the risk of developing cardiovascular disease. Excess cholesterol in the blood has been linked to the progression of atherosclerosis, and cholesterol testing is therefore now considered a first-line test for preventing cardiovascular disease.
When is it requested?
Cholesterol testing is a screening test that all adults should have at least once every five years; it is requested together with HDL cholesterol, LDL cholesterol and triglycerides, which together make up the lipid profile.
Total cholesterol is measured more often if other major cardiovascular risk factors are present or to monitor cholesterol-lowering treatment.
What does the test result mean?
According to the NCEP ATP-III guidelines, total cholesterol values fall into three risk categories: values below 200 mg/dL are considered desirable and reflect a low risk of cardiovascular disease; values between 200 and 240 mg/dL reflect a moderate cardiovascular risk; if total cholesterol is above 240 mg/dL, the risk is high. In any case, the result must be interpreted together with the other lipid profile results; the doctor will then decide whether and how to intervene. Treatment will be decided once the causes of the high cholesterol are known. During treatment, repeating the test can be useful to follow its effects and identify the most suitable treatment. The target value, i.e. the cholesterol level to aim for with treatment, must be decided by the doctor, usually on the basis of LDL cholesterol.
Is there anything else I should know?
Cholesterol can be significantly low in severe liver disease, malnutrition and cachexia. Cholesterol does not change in response to a single meal, but only after a prolonged change in the fat content of the diet; in any case, several weeks are needed before changes in cholesterol can be seen.
It is not yet clear whether very low cholesterol levels (less than 100 mg/dL) can be harmful; this is usually seen together with malnutrition, liver disease or cancer.
1. Who should be screened for cholesterol?
2. What causes high cholesterol?
3. Which medicines are used to treat high cholesterol?
4. What is the cardiovascular risk associated with high cholesterol?
5. Why can cholesterol rise even without changes in diet or daily physical activity?
6. Why do some doctors prefer to repeat the test after a few months when cholesterol is high, rather than starting medicines straight away?
1. Who should be screened for high cholesterol?
Everyone over 30 should be screened for high cholesterol, ideally as part of a lipid profile, at least once every five years.
2. What causes high cholesterol?
High cholesterol can result from an inherited defect or, more commonly, from a family predisposition and/or a diet rich in saturated fat. It can also be secondary to other conditions, such as hypothyroidism.
3. Which medicines are used to treat high cholesterol?
The best treatment is a diet low in saturated fat, which can lower cholesterol. If diet is not enough, medicines can be used. When cholesterol is particularly high, the doctor may decide to combine two different medicines. There are several classes of medicines used to treat high cholesterol: the most widely used are HMG-CoA reductase inhibitors (statins), along with resins (colestyramine, colestipol) that block the enterohepatic circulation of bile salts. In any case, the choice of the most suitable medicine is up to the doctor and depends on the patient’s medical history.
4. What is the cardiovascular risk associated with high cholesterol?
Cholesterol is linearly related to cardiovascular risk; however, there are many other risk factors, such as smoking, diabetes mellitus, age and high blood pressure.
5. Why can cholesterol rise even without changes in diet or daily physical activity?
Cholesterol levels can vary over time, so much so that changes of up to 10% can be seen from one month to the next; these changes are normal and reflect normal fat metabolism.
6. Why do some doctors prefer to repeat the test after a few months when cholesterol is high, rather than starting medicines straight away?
Cholesterol levels can vary over time, and a single measurement may not be enough to establish the true cholesterol value. It is therefore advisable to take at least two measurements a few months apart before starting any treatment, which should in any case be based on the average of the two measurements.