Advanced Lipid Testing Helps Predict Cardiovascular Disease Risk

I caught up recently with Dr. Michael Twyman, board-certified cardiologist on staff at Des Peres Hospital, to talk about advance lipid testing and it's role in preventive cardiology and his work with patients in reducing their cardiac risk factors.

"Cholesterol is a type of fat (lipid), produced by the liver and found in certain foods," said Dr. Twyman. "The body uses this waxy substance to make vitamin D and certain hormones, build cell walls, and provide bile salts involved in fat digestion. All the cholesterol the body needs comes from the liver. But because cholesterol is found in so many foods, some people can have too much cholesterol circulating in their blood. This could lead to serious problems such as heart disease."

Dr. Twyman explained that there are different forms of cholesterol. LDL, low-density lipoprotein or “bad”, cholesterol can accumulate in blood vessel walls, eventually clog arteries, and potentially develop blood clots and cause a heart attack. HDL, high-density lipoprotein or “good”, cholesterol helps remove cholesterol from blood vessels, and carries it back to the liver where it is processed and eventually removed from the body. Triglycerides are another form of fat in the bloodstream and fat tissues that can contribute to the hardening and narrowing of the arteries.

A standard blood-cholesterol test checks for total cholesterol, LDL, HDL and triglycerides. Dr. Twyman gave a breakdown of the ranges for each:

• For total cholesterol, results less than 200 milligrams per deciliter (mg/dL are considered normal, 201 to 240 mg/dL is borderline, and more than than 240 mg/dL is high.
• For HDL, more of which is better, 60 mg/dL is good because it protects against heart disease, 40 to 50 mg/dL is acceptable, and less than 40 mg/dL is low, which increases the risk for heart disease.
• For LDL, for which lower is better, less than 100 mg/dL is optimal, 100 to 129 mg/dL is near-optimal, 130 to 159 mg/dL is borderline high, 160 to 189 mg/dL is high, and 190 mg/dL or higher is very high.
• For triglycerides, normal levels are below 150 mg/dL; over 200 mg/dL are considered high.

"While these numbers are useful in getting an overview of a person’s risk for heart disease," said Twyman, "sometimes doctors need to order an advanced lipid profile to improve the ability to predict cardiovascular disease risk and optimize cholesterol treatment.  Apolipoprotein B (apoB) and LDL particle number (LDL-P) are two commonly used advanced lipid tests that may be recommended for people who have low HDL cholesterol and metabolic risk factors." 

Both apoB and LDL-P are simple blood tests that do not require fasting. LDL-P measures the size as well as number of LDL particles that carry LDL cholesterol per liter of plasma. This information is used to help diagnose the cause of a cholesterol abnormality. A higher number of small, dense LDL particles, for example, could be caused by insulin resistance, which increases the risk for developing diabetes. The concentration of lipoprotein particles with apolipoprotein B on their surface is measured in an apoB test. Particles labeled with one molecule of apo B have the potential to cause disease.

Dr Twyman explained that specific target numbers for test results will depend on a patient's risk factors. Overall, cholesterol can be lowered by taking certain medications, exercising, avoiding saturated fat, not smoking, and eating more fiber, fish and nuts.

For more information about advanced lipid testing, talk with your doctor or visit the National Lipid Association website at www.learnyourlipids.com.