Test Library

• Screening: for young adults, every five years;
• Screening for adults age >35 years;  every year
• for youths, once between the ages of 9 and 11 and again between ages 17 and 21
• Monitoring: at regular intervals when risk factors are present, when prior results showed high risk levels, and/or to monitor effectiveness of treatment

A blood sample is obtained by inserting a needle into a vein in your arm.

Test Preparation Needed?

Typically, fasting for 10-12 hours before having your blood drawn is required; only water is permitted.

Lipids are a group of fats and fat-like substances that are important constituents of cells and sources of energy. A lipid profile measures the level of specific lipids in the blood.

Two types of lipids, cholesterol and triglycerides, are transported in the blood by lipoprotein particles. Each particle contains a combination of protein, cholesterol, triglyceride, and phospholipid molecules. The particles measured with a lipid profile are classified by their density into high-density lipoproteins (HDL), low-density lipoproteins (LDL), and very low-density lipoproteins (VLDL).

Monitoring and maintaining healthy levels of these lipids is important in staying healthy. While the body produces the cholesterol needed to function properly, the source for some cholesterol is the diet. Eating too much of foods that are high in cholesterol, saturated fats, and trans unsaturated fats (trans fats) or having an inherited predisposition can result in a high level of cholesterol in the blood. The extra cholesterol 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 increasing the risk of numerous health problems, including heart disease and stroke. A high level of triglycerides in the blood is also associated with an increased risk of developing cardiovascular disease (CVD), although the reason for this is not well understood.

A lipid profile typically includes:

• Total cholesterol —this test measures all of the cholesterol in all the lipoprotein particles.
• High-density lipoprotein cholesterol (HDL-C) — measures the cholesterol in HDL particles; often called “good cholesterol” because it removes excess cholesterol and carries it to the liver for removal.
• Low-density lipoprotein cholesterol (LDL-C) — calculates the cholesterol in LDL particles; often called “bad cholesterol” because it deposits excess cholesterol in walls of blood vessels, which can contribute to atherosclerosis. Usually, the amount of LDL cholesterol (LDL-C) is calculated using the results of total cholesterol, HDL-C, and triglycerides.
• Triglycerides — measures all the triglycerides in all the lipoprotein particles; most is in the very low-density lipoproteins (VLDL).

Some other information may be reported as part of the lipid profile. These parameters are calculated from the results of the tests identified above.

• Very low-density lipoprotein cholesterol (VLDL-C) — calculated from triglycerides/5; this formula is based on the typical composition of VLDL particles.
• Cholesterol/HDL ratio — calculated ratio of total cholesterol to HDL-C.

A blood sample is obtained by inserting a needle into a vein in the arm. Sometimes a drop of blood is collected by puncturing the skin.

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

Typically, fasting for 10-12 hours before having the blood sample drawn is required; only water is permitted.

How is it used?

The lipid profile is used as part of a cardiac risk assessment 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 of heart disease to develop a plan of 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.

When is it ordered?

Adults

It is recommended that healthy adults with no other risk factors for heart disease be tested with a fasting lipid profile once every five years. Initial screening may involve only a single test for total cholesterol and not a full lipid profile. However, if the screening cholesterol test result is high, it will likely be followed by testing with a lipid profile.

If other risk factors are present or if previous testing revealed a high cholesterol level in the past, more frequent testing with a full lipid profile is recommended.

Risk factors other than high low-density lipoprotein cholesterol (LDL-C) include:

• Cigarette smoking
• Age (if you are a male 45 years or older or a female 50-55 years or older)
• Low HDL cholesterol (less than 40 mg/dL (1.04 mmol/L))
• Hypertension (blood pressure of 140/90 or higher or taking high blood pressure medications)
• Family history of premature heart disease (heart disease in a first degree male relative under age 55 or a first degree female relative under age 65)
• Diabetes

 

Note: High HDL (60 mg/dL or above) is considered a “negative risk factor” and its presence allows the removal of one risk factor from the total.

Youths

For children and adolescents, routine lipid testing is recommended by the American Academy of Pediatrics (AAP) once between the ages of 9 and 11 and again between 17 and 21. 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. High-risk children should be tested between 2 and 8 years old, according to the AAP. Children younger than 2 years old are too young to be tested.

A lipid profile may also 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.

Adults

In general, a doctor will take into consideration the results of each component of a lipid profile plus other risk factors to determine whether treatment is necessary and, if so, which treatment will best help to lower a person’s risk of heart disease. The National Cholesterol Education Program offers the following guidelines for adults for classifying results of the tests:

LDL Cholesterol
Optimal: Less than 100 mg/dL (2.59 mmol/L)
Near/above optimal: 100-129 mg/dL (2.59-3.34 mmol/L)
Borderline high: 130-159 mg/dL (3.37-4.12 mmol/L)
High: 160-189 mg/dL (4.15-4.90 mmol/L)
Very high: Greater than 190 mg/dL (4.90 mmol/L)

Total Cholesterol
Desirable: Less than 200 mg/dL (5.18 mmol/L)
Borderline high: 200-239 mg/dL (5.18 to 6.18 mmol/L)
High: 240 mg/dL (6.22 mmol/L) or higher

HDL Cholesterol
Low level, increased risk: Less than 40 mg/dL (1.0 mmol/L) for men and less than 50 mg/dL (1.3 mmol/L) for women
Average level, average risk: 40-50 mg/dL (1.0-1.3 mmol/L) for men and between 50-59 mg/dl (1.3-1.5 mmol/L) for women
High level, less than average risk: 60 mg/dL (1.55 mmol/L) or higher for both men and women

Fasting Triglycerides
Desirable: Less than 150 mg/dL (1.70 mmol/L)
Borderline high: 150-199 mg/dL(1.7-2.2 mmol/L)
High: 200-499 mg/dL (2.3-5.6 mmol/L)
Very high: Greater than 500 mg/dL (5.6 mmol/L)

Youths

A full lipid panel is recommended for screening youths, according to the American Academy of Pediatrics. Fasting prior to lipid screening in children is unnecessary. To avoid fasting, a non-high-density lipoprotein cholesterol (non-HDL-C) level is calculated by testing for total cholesterol and HDL-C and taking the difference between the two levels. Recommended cut-off values include:

	Test	Acceptable (mg/dL)	Borderline (mg/dL)	High (mg/dL)
Children and Adolescents	Total Cholesterol	Less than 170	170-199	Greater than or equal to 200
	Non-HDL Cholesterol	Less than 120	120-144	Greater than or equal to 145
Young Adults	Total Cholesterol	Less than 190	190-224	Greater than or equal to 225
	Non-HDL Cholesterol	Less than 150	150-189	Greater than or equal to 190

*Adapted from “Expert panel on integrated guidelines for cardiovascular health and risk reduction in children and adolescents: Summary report.” Pediatrics 2011; 128.

There is increasing interest in measuring triglycerides in people who have not fasted. The reason is that a non-fasting sample may be more representative of the “usual” circulating level of triglyceride since most of the day, blood lipid levels reflect post-meal (post-prandial) levels rather than fasting levels. However, it is not yet certain how to interpret non-fasting levels for evaluating risk, so at present there is no change in the current recommendations for fasting prior to tests for lipid levels.

A routine cardiac risk assessment typically includes a fasting lipid profile.

1.  How is treatment determined?

Treatment is determined by your overall risk of coronary heart disease. Based on the results of lipid tests and other major risk factors, your target LDL cholesterol is identified. If your LDL-C is above the target value, you will be treated.

Your target LDL-C value is:

• Less than 100 mg/dL (2.59 mmol/L) if you have heart disease or diabetes [and ideally < 70 mg/dL (1.81 mmol/L)]
• Less than 130 mg/dL (3.37 mmol/L) if you have 2 or more risk factors
• Less than 160 mg/dL (4.14 mmol/L) if you have 0 or 1 risk factor

The first step in treating high LDL-C is targeted at changes in lifestyle, specifically, adopting diets low in cholesterol, saturated fat and trans unsaturated fats (trans fats) 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-C. You may be prescribed one of these. Your LDL-C 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.

2.  My lipid profile results came back with high triglycerides and no results for LDL-cholesterol. Why?

In most screening lipid profiles, LDL-cholesterol is calculated from the other lipid measurements. However, the calculation is not valid if triglycerides are over 400 mg/dL (4.52 mmol/L). To determine LDL-cholesterol when triglycerides are over 400 mg/dL (4.52 mmol/L) requires special testing techniques such as a lipid ultracentrifugation test (sometimes called a beta-quantification test).

3.  What is non-HDL-cholesterol?

Non-HDL-cholesterol (non-HDL-C) is calculated by subtracting your HDL-C result from your total cholesterol result. It represents the “atherogenic” cholesterol — the cholesterol that can build up in the arteries, form plaques, and cause narrowing of the vessels and blockages. Unlike calculation of LDL-C (see Question #3 above), this calculation is not affected by high levels of triglycerides. Your non-HDL-C result may be used to assess your risk for CVD, especially if you have high triglycerides, since high non-HDL-C is associated with increased risk. As recommended by the National Cholesterol Education Program, Adult Treatment Plan III, if you have high triglycerides (greater than 200 mg/dL), the non-HDL-C result can be used as a secondary target of treatments such as lifestyle changes and drugs that aim to lower lipid levels.

5.  What is a low-density lipoprotein particle number (LDL-P) test?

LDL-P is a test that measures the number of LDL particles, rather than measuring the amount of LDL-cholesterol. For many people, the LDL-C test is a good indicator of risk of CVD. However, research has found that some people with healthy levels of LDL-C still have increased risk of CVD. Similarly, individuals with some chronic conditions such asdiabetes may have increased risk though their LDL-C is at a healthy level. For these populations, it has been suggested that the number of LDL particles, and their size, might be an additional factor to consider when determining their CVD risk.