Ask Dr. K: Advanced cholesterol testing useful for some

Cholesterol is a waxy, yellowish fat. It travels through your bloodstream in tiny, protein-covered particles called lipoproteins. These particles contain cholesterol and triglycerides, a type of fat.

The smallest and densest particles are high-density lipoproteins (HDL). Also known as “good” cholesterol, HDL removes cholesterol from artery walls. Low-density lipoprotein (LDL) particles are known as “bad” cholesterol. They add cholesterol to the artery walls. There, it creates artery-clogging plaque that can trigger a heart attack or stroke.

Most doctors use LDL levels to predict heart attack risk. But many people with heart disease have LDL levels that aren’t especially high.

It turns out that not all LDL particles are created equal. Larger, fluffier LDL particles may have a harder time getting into arteries. Smaller, more tightly packed LDL may have an easier time getting into arteries, making them more dangerous. And a particular protein on LDL — apoB — further increases heart disease risk. Advanced cholesterol tests measure LDL sub-particles as well as apoB.

My colleague Dr. Jorge Plutzky is director of the Lipid/Prevention Clinic and co-director of Preventive Cardiology at Harvard-affiliated Brigham and Women’s Hospital. He says that for the average person, the additional detail from advanced lipid testing isn’t critical. It wouldn’t change the treatment a doctor would have otherwise recommended.

Why does he say that? Because there are plenty of new tests that have theoretical value in determining a person’s risk of heart disease and stroke. But they should be considered standard, generally recommended tests only if they actually make the prediction of risk more accurate.

For a new test to become standard, it needs to be used along with standard tests in thousands of people. Those people then are followed for many years. Some will develop heart disease or have a stroke, and some will not. The standard tests, since they’ve already been proven, will do a good job. While they won’t be perfect, they will identify people who are more likely to develop disease.

But will the new test, when added to the standard tests, make that prediction even more accurate? That’s what has to be shown for doctors to use the new test.

Dr. Plutzky thinks that advanced cholesterol testing might help to better understand heart disease risk in certain groups of people. These include people with:

— A history of cardiovascular disease (CVD) without obvious risk factors (such as high blood pressure or diabetes);

— A history of CVD before age 55 in men or before age 65 in women;

— A parent or sibling with early heart disease.

Whatever you decide about the test, don’t forget tried-and-true strategies for lowering heart disease risk. These include eating a healthy diet, exercising regularly and maintaining a healthy weight.

To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.