Dr Leigh Martens

General Practitioner

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Blood-tests Explained


Disclaimer:

This website is intended to assist with patient education and should not be used as a diagnostic, treatment or prescription service, forum or platform. Always consult your own healthcare practitioner for a more personalised and detailed opinion

Cholesterol


At a Glance

Why Get Tested?

To screen for risk of developing heart disease; to monitor effectiveness of lipid-lowering therapy

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; adults should be tested once every four to six years; children, teens, and young adults should be tested once between the ages of 9 and 11 and then again between the ages of 17 and 21.

Monitoring: may be done more frequently and at regular intervals when risk factors for heart disease are present, when prior results showed high risk levels, and/or when undergoing treatment for unhealthy lipid levels

Sample Required?

A blood sample drawn from a vein in your arm or from a fingerstick

Test Preparation Needed?

If you are having this test performed as part of the lipid profile, typically you will need to fast for 9-12 hours before the sample is collected; only water is permitted. Your healthcare practitioner may decide that you may be tested without fasting. Follow any instructions you are given and tell the person drawing your blood whether or not you have fasted. For youths without risk factors, testing may be done without fasting.

The Test Sample

What is being tested?

Cholesterol is a substance (a steroid) that is essential for life. It forms the membranes for cells in all organs and tissues in the body. It is used to make hormones that are essential for development, growth, and reproduction. It forms bile acids that are needed to absorb nutrients from food. The test for cholesterol measures total cholesterol that is carried in the blood by lipoproteins.

A small amount of cholesterol circulates in the blood in complex particles called lipoproteins. Each particle contains a combination of protein, cholesterol, triglyceride, and phospholipid molecules and the particles are classified by their density into high-density lipoproteins (HDL), low-density lipoproteins (LDL), and very low-density lipoproteins (VLDL). HDL-C particles, sometimes called "good" cholesterol, carry excess cholesterol away for disposal and LDL-C particles, or "bad" cholesterol, deposit cholesterol in tissues and organs.

Monitoring and maintaining healthy levels of cholesterol is important for staying healthy. The body produces the cholesterol needed to work properly, but the source for some cholesterol is diet. If an individual has an inherited predisposition for high cholesterol levels or eats too much of the foods that are high in saturated fats and trans unsaturated fats (trans fats), then the level of cholesterol in that person's blood may increase and have a negative impact on the person's health. The extra cholesterol in the blood may be deposited in plaques on the walls of blood vessels. Plaques can narrow or eventually block the opening of blood vessels, leading to hardening of the arteries (atherosclerosis) and increased risk of numerous health problems, including heart disease and stroke.

How is the sample collected for testing?

Most often, a blood sample is collected from a vein in the arm. Sometimes cholesterol is measured using a drop of blood collected by puncturing the skin on a finger. A fingerstick sample is typically used when cholesterol is being measured on a portable testing device, for example, at a health fair.

Is any test preparation needed to ensure the quality of the sample?

Cholesterol tests typically require fasting for 9-12 hours before the test; only water is permitted. Your healthcare practitioner may decide that you may be tested without fasting. Follow any instructions you are given and tell the person drawing your blood whether or not you have fasted. For youths without risk factors, testing may be done without fasting.

The Test

How is it used?

The test for total cholesterol is used alone or as part of a lipid profile to help predict an individual's risk of developing heart disease and to help make decisions about what treatment may be needed if there is borderline or high risk. As part of a lipid profile (which includes other tests for high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides), it may also be used to monitor the effectiveness of treatment once it is initiated.

Because high blood cholesterol has been associated with hardening of the arteries (atherosclerosis), heart disease, and a raised risk of death from heart attacks, cholesterol testing is considered a routine part of preventive healthcare.

Results of the cholesterol test and other components of the lipid profile are used along with other known risk factors of heart disease to develop a plan of treatment and follow-up. Treatment options may include lifestyle changes such as diet or exercise programs or lipid-lowering drugs such as statins.

When is it ordered?

Adults

Cholesterol testing is recommended as a screening test to be done for all adults with no risk factors for heart disease at least once every four to six years. It is frequently done in conjunction with a routine physical exam.

Cholesterol is tested at more frequent intervals (often several times per year) when a person has one or more risk factors for heart disease. Major risk factors include:

  • Cigarette smoking
  • Being overweight or obese
  • Having an unhealthy diet
  • Being physically inactive (not getting enough exercise)
  • Age (men 45 years or older or women 55 years or older)
  • Having high blood pressure (hypertension) or taking high blood pressure medications
  • Family history of premature heart disease (heart disease in an immediate family member—male relative under age 55 or female relative under age 65)
  • Having pre-existing heart disease or already having had a heart attack
  • Having diabetes or prediabetes

Youth

Screening for high cholesterol as part of a lipid profile is recommended for children and young adults. They should be tested once between the ages of 9 and 11 and then again between the ages of 17 and 21. Earlier and more frequent screening with a lipid profile is recommended for children and youths who are at an increased risk of developing heart disease as adults. Some of the risk factors are similar to those in adults and include a family history of heart disease or health problems such as diabetes, high blood pressure, or being overweight. When the youth's body mass index (BMI) is at or above the 85th percentile, cholesterol testing is recommended. For an obese youth (one whose BMI is at or above the 95th percentile), laboratory tests to measure cholesterol levels may be recommended every 2 years.

High-risk children should have their first cholesterol test between 2 and 8 years of age, according to the American Academy of Pediatrics. Children younger than 2 years old are too young to be tested. If the initial results are not worrisome, the fasting test should be done again in three to five years.

Monitoring

As part of a lipid profile, total cholesterol tests may be ordered at regular intervals to evaluate the success of lipid-lowering lifestyle changes, such as diet and exercise, or to determine the effectiveness of drug therapy such as statins. Guidelines from the American College of Cardiology (ACC) and the American Heart Association (AHA) recommend that adults taking statins have a fasting lipid profile done 4 to 12 weeks after starting therapy and then every 3 to 12 months thereafter to assure that the drug is working.

What does the test result mean?

In general, healthy lipid levels help to maintain a healthy heart and lower the risk of heart attack or stroke. A healthcare practitioner will take into consideration total cholesterol results and the other components of a lipid profile as well as other risk factors to help determine a person's overall risk of heart disease, whether treatment is necessary and, if so, which treatment will best help to lower the person's risk.

In 2002, the National Cholesterol Education Program (NCEP) Adult Treatment Panel III (ATP III) provided the guidelines for evaluating lipid levels and determining treatment. However, in 2013, the ACC and AHA issued guidelines for adults that made recommendations on who should receive cholesterol-lowing therapy. (For more details, see the Lipid Profile article).

However, use of the updated guidelines remains controversial. Many still use the older guidelines from the NCEP ATP III to evaluate lipid levels and cardiovascular disease (CVD) risk:

For adults, in a routine setting where testing is done to screen for risk, the test results are grouped in three categories of risk:

  • Desirable: A cholesterol below 200 mg/dL (5.18 mmol/L) is considered desirable and reflects a low risk of heart disease.
  • Borderline high: A cholesterol of 200 to 239 mg/dL (5.18 to 6.18 mmol/L) is considered to reflect moderate risk. If the cholesterol test was done by itself, a healthcare practitioner may decide to order a lipid profile to see if the high cholesterol is due to the amount of bad cholesterol (high LDL-C) or good cholesterol (high HDL-C). Depending on the results of the lipid profile (and any other risk factors), a decision will be made about whether treatment, including lifestyle changes, is necessary.
  • High risk: A cholesterol greater than or equal to 240 mg/dL (6.22 mmol/L) is considered high risk. A health care provider may order a lipid profile (as well as other tests) to try to determine the cause of the high cholesterol. Once the cause is known, an appropriate treatment will be prescribed.

For children and adolescents:

  • A cholesterol below 170 mg/dL (4.40 mmol/L) is acceptable.
  • A result of 170-199 mg/dL (4.40-5.16 mmol/L) is borderline.
  • A total cholesterol reading greater than or equal to 200 mg/dL (5.17 mmol/L) is considered high.

For young adults:

  • A cholesterol below 190 mg/dL (4.92 mmol/L) is acceptable.
  • A result of 190-224 mg/dL (4.92-5.80 mmol/L) is borderline.
  • A total cholesterol greater than or equal to 225 mg/dL (5.82 mmol/L) is considered high.

In a treatment setting, testing is used to see how much cholesterol is decreasing as a result of treatment. The target value is usually based on LDL-C, according to ATP III.

Is there anything else I should know?

Cholesterol should be measured when a person is not ill. Blood cholesterol is temporarily low during acute illness, immediately following a heart attack, or during stress (like from surgery or an accident). Wait at least six weeks after any illness to have cholesterol measured.

There is some debate about whether very low cholesterol is bad. Low cholesterol (less than 100 mg/dL (2.59 mmol/L)) is often seen when there is an existing problem like malnutrition, liver disease, or cancer. However there is no evidence that low cholesterol causes any of these problems.

Cholesterol is typically high during pregnancy. Women should wait at least six weeks after having a baby to have cholesterol measured.

Some drugs that are known to increase cholesterol levels include anabolic steroids, beta blockers, epinephrine, oral contraceptives, and vitamin D.