Blood Cholesterol

 

Medical Illustration of Atherosclerosis

 

Cholesterol plays a major role in a person's heart health. High blood cholesterol is a major risk factor forcoronary heart disease and stroke.

That's why it's important to know yourcholesterol levels. You should also learn about other risk factors for heart disease and stroke.

How is cholesterol tested?

A cholesterol screening measures your level of high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol and triglycerides. A small sample of blood will be drawn from your arm. If your doctor orders other tests to be run at the same time as your cholesterol test, all the samples are usually taken at the same time. Your blood sample is then analyzed in a laboratory.

Your doctor will tell you if you should fast (avoid consuming food, beverages and medications, usually for nine to 12 hours) before your blood test. If you aren't fasting when the blood sample is drawn, only the values for total cholesterol and HDL cholesterol will be usable. That's because the amount of LDL (bad) cholesterol level and triglycerides can be affected by what you've recently consumed.

Your test report will show your cholesterol level in milligrams per deciliter of blood (mg/dL). Your doctor will interpret your cholesterol numbers based on other risk factors such as age, family history, smoking and high blood pressure.

What do your cholesterol levels mean?

How often should I have my cholesterol checked?

If you are age 20 or older and have not been diagnosed with cardiovascular disease, the American Heart Association recommends having your cholesterol levels checked every four to six years as part of a cardiovascular risk assessment.

You may need to have your cholesterol and other risk factors assessed more often if your risk is elevated.

Your healthcare provider will talk with you about what your results mean and discuss appropriate treatment options based on your cardiovascular risk and overall health.

Where should I have my cholesterol checked?

It's best to have your primary care doctor run your cholesterol test. Other risk factors such as your age, family history  smoking history and blood pressure must be considered when interpreting your results and your primary care doctor is most likely to have all that information. Once you know your numbers, your doctor can recommend a treatment and prevention plan, as well as follow-up testing.

If you have your cholesterol checked at public screenings, make sure a reputable company does the screening. Remember that your cholesterol level is just part of your overall cardiovascular risk profile, and your other risk factors must be considered. You should share the screening results with your healthcare professional so your tests can be properly interpreted, and an appropriate treatment and prevention plan developed.

The American Heart Association hasn't taken a position on cholesterol home testing devices. Several devices are on the market. Some measure only total cholesterol. Others measure total cholesterol and HDL (good) cholesterol. One measures LDL (bad) cholesterol, HDL cholesterol and triglycerides (blood fats).

 
What is a cardiac risk assessment?
 
This is a group of tests and health factors that have been proven to indicate a person's chance of having a cardiovascular event such as a heart attack or stroke. They have been refined to indicate the degree of risk: slight, moderate, or high.
 
What is included in a routine cardiac risk assessment? 
Perhaps the most important indicators for cardiac risk are those of a person's personal health history. These include:
 
  • Age
  • Family history
  • Weight
  • Cigarette smoking
  • Blood pressure
  • Diet
  • Exercise, physical activity
  • Diabetes
There are some imaging tests that may be used in cardiac risk assessment. Non-invasive tests may include, for example, an electrocardiogram (ECG, EKG) or a stress test, also called ECG stress test or metabolic stress test. Invasive tests may also be used to evaluate for the presence of cardiovascular disease (CVD), but they are usually used for diagnostic purposes in people with signs and symptoms and not for risk assessment. Examples include an angiography/arteriography and cardiac catheterization. (For more on these, see the Mayo Clinic's webpage on Coronary artery disease: Tests and diagnosis.)
 
The lipid profile is the most important blood test for cardiac risk assessment.
 
How is the lipid profile used? 
The lipid profile is used to help determine an individual's risk of heart disease and to help make decisions about what treatment may be best if there is borderline or high risk. The results of the lipid profile are considered along with other known risk factors for heart disease to develop a plan for treatment and follow-up. Depending on the results and other risk factors, treatment options may involve lifestyle changes such as diet and exercise or lipid-lowering medications such as statins.
 
The lipid profile measures cholesterol, triglycerides, high density lipoprotein cholesterol (HDL-C, "good" cholesterol) as well as calculates low density lipoprotein cholesterol (LDL-C, "bad" cholesterol). Triglycerides are a form of fat and a major source of energy for the body. Below are the desirable ranges for the components of the lipid profile:
 
  • Cholesterol <200 mg/dL (5.18 mmol/L)
  • HDL-cholesterol > 40 mg/dL (1.04 mmol/L)
  • LDL-cholesterol <100 mg/dL* (2.59 mmol/L)
  • Triglycerides <150 mg/dL (1.70 mmol/L)
 
* optimal; levels will depend on the number and type of risk factors present and why testing is being done 
Some other information may be reported as part of the lipid profile. These parameters are calculated from the results of the tests identified above.
 
Non-HDL-C — calculated by subtracting the HDL-C result from the total cholesterol result; this is considered to be the portion of cholesterol that is most likely to lead to hardening of the arteries (atherosclerosis). 
 
Very low-density lipoprotein cholesterol (VLDL-C) — calculated by dividing the triglyceride value by 5 (if in mg/dL, or by 2.2 if in mmol/L); this formula is based on the typical composition of VLDL particles; there is growing evidence that VLDL-C plays an important role in the process that leads to the formation of plaques in arteries.
 
Cholesterol/HDL ratio — calculated by dividing the HDL-C result into the total cholesterol result; a higher ratio indicates a higher risk of heart disease while a lower ratio indicates a lower risk.
 
 
What other tests may be used to assess cardiac risk? 
Some other tests that may be used to assess cardiac risk include:
 
High-sensitivity C-reactive protein (hs-CRP):
 
Studies have shown that measuring CRP with a high sensitivity test can help identify risk of CVD. This test is different from the regular CRP test, which detects elevated levels of CRP in people with infections and inflammatory diseases. The hs-CRP test measures CRP that is in the normal range for healthy people. It can be used to distinguish people with low normal levels from people with high normal levels. High normal levels of hs-CRP in otherwise healthy individuals have been found to be predictive of the future risk of heart attack, stroke, sudden cardiac death, and peripheral arterial disease, even when lipid levels are within acceptable ranges. Several groups have recommended that this test be used for people with moderate risk of heart attack over the next 10 years; however, there is not a consensus on how the test should be used otherwise, nor on how frequently the test should be repeated.
 
Lipoprotein A (Lp(a)): Lp(a) is a lipoprotein consisting of an LDL molecule with another protein (Apolipoprotein (a)) attached to it. Lp(a) is similar to LDL-C but does not respond to typical strategies to lower LDL-C such as diet, exercise, or most lipid-lowering drugs. Since the level of Lp(a) appears to be genetically determined and not easily altered, the presence of a high level of Lp(a) may be used to identify individuals who might benefit from more aggressive treatment of other risk factors.
Several other tests are being studied for their usefulness in determining cardiac risk. Currently, there is no consensus or formal recommendations for them. A health practitioner may order one or more of these tests to help assess someone's risk.
 
Some of these include:
 
  • LDL particle testing (LDL-P) (number and size)
  • Lp-PLA2
  • Homocysteine
  • GGT
  • Urine albumin (microalbumin)
  • Cystatin C
  • Fibrinogen
  • Apo A-I
  • Apo B
  • APOE Genotyping (CVD)
  • MTHFR Mutation
 
How is treatment determined? 
Treatment is based on many factors, including the results of the lipid profile and a person's family and personal medical and lifestyle history.
 
Is there anything else I should know? 
 
A healthy diet and exercising are important in reducing blood pressure, cholesterol, and triglycerides. Sometimes these lifestyle changes are not sufficient to reach desirable levels. There are also drugs (statins) that are effective in lipid management. Some conditions involving elevated lipids levels are hereditary. High lipid levels in these conditions cannot always be lowered sufficiently by diet and exercise. This type of elevation usually requires treatment with lipid-lowering drugs.
 
Common Questions
 
 
1. Are some people more at risk for a heart attack than others?
Yes. Those who are overweight, smoke cigarettes, have high blood pressure (hypertension) or diabetes, have abnormal cardiac risk test results, and those with a family history of heart disease are at greater risk.
 
2. Are there home test kits for determining if I am at risk for a heart attack?
 
No. Your overall cardiac risk is based on a number of factors, including your personal health history as well as the results of any or all of the tests mentioned previously. An assessment requires interpretation by a trained medical professional. However, there are resources available to help you better understand your risk. For example, the American Heart Association offers a heart attack assessment online tool. And there are home tests available to measure your cholesterol. (For more on home cholesterol testing, see the Mayo Clinic article Are home cholesterol test kits accurate?)
 
 
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