Lipid Profile

Common Questions

1. I had a screening test for cholesterol. It was less than 200 mg/dL (5.18 mmol/L). Do I need a lipid profile?
If your total cholesterol is below 200 (5.18 mmol/L) and you have no family history of heart disease or other risk factors, a full lipid profile is probably not necessary. However, an HDL-cholesterol measurement would be advisable to assure that you do not have a low HDL. Many screening programs now offer both cholesterol and HDL.

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 direct LDL-C test or a lipid ultracentrifugation test (sometimes called a beta-quantification test).

3. What is VLDL?
Very Low Density Lipoprotein (VLDL) is one of three major lipoprotein particles. The other two are high density lipoprotein (HDL) and low density lipoprotein (LDL). Each one of these particles contains a mixture of cholesterol, protein, and triglyceride, but in varying amounts unique to each type of particle. LDL contains the highest amount of cholesterol. HDL contains the highest amount of protein. VLDL contains the highest amount of triglyceride. Since VLDL contains most of the circulating triglyceride and since the composition of the different particles is relatively constant, it is possible to estimate the amount of VLDL cholesterol by dividing the triglyceride value (in mg/dL) by 5. At present, there is no simple, direct way of measuring VLDL-cholesterol, so the estimate calculated from triglyceride is used in most settings. This calculation is not valid when the triglyceride is greater than 400 mg/dl (see question 2 above). Increased levels of VLDL-cholesterol have been found to be associated with increased risk of heart disease and stroke.

4. 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 VLDL-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.

 

Is there anything else I should know?

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.