Cholesterol

Cholesterol test is performed to screen for risk of developing heart disease.

Cholesterol is different from most tests in that it is not used to diagnose or monitor a disease but is used to estimate risk of developing a disease — specifically heart disease. Because high blood cholesterol has been associated with hardening of the arteries, heart disease and a raised risk of death from heart attacks, cholesterol testing is considered a routine part of preventive health care.

Cholesterol testing is recommended as a screening test to be done on all adults at least once every five years. It is usually ordered as part of a routine physical exam. It may be ordered alone or in combination with other tests including HDL , LDL , and triglycerides — often called a lipid profile .

Cholesterol is tested at more frequent intervals (often several times per year) in patients who have been prescribed diet and/or drugs to lower their cholesterol. The test is used to track how well these measures are succeeding in lowering cholesterol to desired levels and in turn lowering the risk of developing heart disease .

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 240 mg/dL (5.18 to 6.22 mmol/L) is considered to reflect moderate risk. Your doctor may decide to order a lipid profile to see if your high cholesterol is bad cholesterol (high LDL ) or good cholesterol (high HDL ). Depending on the results of the lipid profile (and any other risk factors you may have) your doctor will decide what to do.
• High Risk: A cholesterol above 240 mg/dL (6.22 mmol/L) is considered high risk. Your doctor may order a lipid profile (as well as other tests) to try to determine the cause of your high cholesterol. Once the cause is known, an appropriate treatment will be prescribed.

In a treatment setting, testing is used to see how much cholesterol is decreasing as a result of treatment. The goal for the amount of change or the final (target) value will be set by your doctor. The target value is usually based on LDL.

Cholesterol should be measured when a person is healthy. Blood cholesterol is temporarily low during acute illness, immediately following a heart attack , or during stress (like from surgery or an accident). You should wait at least 6 weeks after any illness to have cholesterol measured.

It is not necessary to fast when you have a cholesterol test. Cholesterol does not change in response to a single meal. Cholesterol does change in response to changes in long term patterns of eating — like changing from a high fat diet to a low fat diet — but it takes several weeks to see changes in blood cholesterol in response to changes in diet.

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 high during pregnancy . Women should wait at least six weeks after the baby is born to have cholesterol measured.

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

HDL Cholesterol

HDL Cholesterol is performed t o determine risk of developing heart disease. If a high cholesterol is due to high HDL, a person is probably at low risk and further testing or treatment for high cholesterol is not advised.

HDL is usually ordered with other tests, either with cholesterol or as part of a lipid profile , including LDL and triglycerides . The combination of total cholesterol and HDL is very useful for screening for heart disease since it is not necessary to fast for these two tests. In contrast, a more complete lipid profile requires fasting for at least 12 hours

High HDL is better than low HDL. It is usually repor ted as a measured value. If HDL is less than 40 mg/dL (1.04 mmol/L), there is an increased risk of heart disease . A desirable level of HDL is greater than 40 mg/dL (1.04 mmol/L) and is associated with average risk of heart disease. A good level of HDL is 60 mg/dL (1.55 mmol/L) or more and is associated with a less than average risk of heart disease.

Some laboratories report a ratio of total cholesterol to HDL cholesterol. The ratio is obtained by dividing the total cholesterol by the HDL cholesterol. For example, if a person has a total cholesterol of 200 mg/dL and an HDL cholesterol level of 50 mg/dL, the ratio would be stated as 4 (or 4:1). A desirable ratio is below 5 (5:1); the optimum ratio is 3.5 (3.5:1). The American Heart Association recommends that the absolute numbers for total blood cholesterol and HDL cholesterol levels be used because they are more useful than the ratio in determining appropriate treatment for patients.

HDL should be interpreted in the context of the overall findings from the lipid profile and in consultation with your doctor.

HDL cholesterol should be measured when a person is healthy. Cholesterol is temporarily low during acute illness, immediately following a heart attack , or during stress (like from surgery or an accident). You should wait at least 6 weeks after any illness to have cholesterol measured.

In women, HDL cholesterol may change during pregnancy . You should wait at least six weeks after your baby is born to have your HDL-cholesterol measured.

LDL Cholesterol

The test for LDL is used to predict your risk of developing heart disease . Of all the forms of cholesterol in the blood, the LDL cholesterol is considered the most important form in determining risk of heart disease. Treatment decisions are based on LDL values.

LDL levels are ordered as part a lipid profile , along with total cholesterol , HDL , and triglycerides . This profile may be ordered as a screening profile in a healthy person as part of a routine physical exam. A lipid profile may be ordered on someone who has had a high screening cholesterol to see if the total cholesterol is high because of too much LDL.

Elevated levels of LDL indicate risk for heart disease . Treatment (with diet or drugs) for high LDL aims to lower LDL to a target value based on your overall risk of heart disease. Your target value is:

• LDL less than 70 mg/dL (2.59 mmol/L) if you have heart disease or diabetes .
• LDL less than 130 mg/dL (3.37 mmol/L) if you have 2 or more risk factors.
• LDL less than 160 mg/dL (4.14 mmol/L) if you have 0 or 1 risk factor.

Risk factors include cigarette smoking, hypertension, low HDL (< 40 mg/dL; < 1.04 mmol/L), family history, age (male 55 or older; female 65 or older), being overweight, and failure to exercise regularly.

Measurement of LDL generally requires a 12-hour fast—meaning that you must not eat or drink anything that has calories for 12 hours before your blood is drawn. This is because LDL is usually calculated from the results of other tests, including triglycerides, that require fasting. This result may be reported as “Calculated LDL.” Some laboratories can measure LDL directly using a special technology and fasting is not necessary. This test is usually called “Direct LDL.”

LDL cholesterol should be measured when a person is healthy. LDL cholesterol is temporarily low during acute illness, immediately following a heart attack , or during stress (like from surgery or an accident). You should wait at least six weeks after any illness to have LDL cholesterol measured.

In women, cholesterol is high during pregnancy . Women should wait at least six weeks after the baby is born to have LDL cholesterol measured.

Triglycerides

Blood tests for triglycerides are usually part of a lipid profile used to identify the risk of developing heart disease . It is especially important for diabetics to have triglycerides measured as part of any lipid testing since triglycerides increase significantly when blood sugar is out of control.

Lipid profiles , including triglycerides, are recommended as routine tests to evaluate risk of heart disease in healthy adults. The test for triglycerides is not often ordered alone since risk of heart disease is based on cholesterol levels, not triglycerides. However, if you have been found to have high triglycerides and are being treated for it, a triglyceride test may be ordered to see if treatment is working.

A normal level for fasting triglycerides is less than 150 mg/dL (1.70 mmol/L). It is unusual to have high triglycerides without also having high cholesterol . Most treatments for heart disease risk will be aimed at lowering cholesterol. However, the type of treatment used to lower cholesterol may differ depending on whether triglycerides are high or normal.

When triglycerides are very high (greater than 1000 mg/dL (11.30 mmol/L)), there is a risk of developing pancreatitis. Treatment to lower triglycerides should be started as soon as possible.

Testing should be done when you are fasting. For 12 to 14 hours before the test, only water is permitted. In addition, alcohol should not be consumed for the 24 hours just before the test.

If a diabetic's blood sugar levels are out control, triglycerides will be very high.

Triglycerides change dramatically in response to meals, increasing as much as 5 to10 times higher than fasting levels just a few hours after eating. Even fasting levels vary considerably day to day. Therefore modest changes in fasting triglycerides measured on different days are not considered to be abnormal.

Lipid Profile

The lipid profile is a group of tests that are often ordered together to determine risk of coronary heart disease. The tests that make up a lipid profile are tests that have been shown to be good indicators of whether someone is likely to have a heart attack or stroke caused by blockage of blood vessels (hardening of the arteries).

The lipid profile includes total cholesterol, HDL-cholesterol (often called good cholesterol), LDL-cholesterol (often called bad cholesterol), and triglycerides. Sometimes the report will include additional calculated values such as HDL/Cholesterol ratio or a risk score based on lipid profile results, age, sex, and other risk factors.

The lipid profile is used to guide providers in deciding how a person at risk should be treated. The results of the lipid profile are considered along with other known risk factors of heart disease to develop a plan of treatment and follow-up.

Treatment is based on your overall risk of coronary heart disease . A target LDL is identified. If your LDL is above the target value, you will be treated. Target LDL values are:

• LDL less than 70 mg/dL (2.59 mmol/L) if you have heart disease or diabetes .
• LDL less than 130 mg/dL (3.37 mmol/L) if you have 2 or more risk factors.
• LDL less than 160 mg/dL (4.14 mmol/L) if you have 0 or 1 risk factor.

The first step in treating high LDL is targeted at changes in lifestyle - specifically adopting diet s low in saturated fat and participating in moderate exercise. You may be referred to a dietician for advice in making dietary changes.

If low-fat diets and exercise are not adequate to lower LDL-cholesterol to the target value, drug therapy would be the next step. There are several classes of drugs that are effective in lowering LDL. Your LDL will be checked at regular intervals to assure that the drug is working. If the drug does not result in reaching your target LDL-cholesterol, your doctor may increase the amount of drug or possibly add a second drug.