Some doctors and researchers say it is a better predictor of heart disease risk, but many doctors and patients don’t talk about it.
It is a family ritual, the periodic cholesterol test. You wake up and skip breakfast (not even coffee) and sit quietly in the exam room, staring at the ceiling as the phlebotomist inserts a needle into your vein. A few days later, the results appear on your graph.
For decades, primary care doctors and cardiologists have focused on two numbers: LDL, or low-density lipoproteins, known as “bad cholesterol,” and HDL, or high-density lipoproteins, also known as “good cholesterol.” Two numbers are considered key determinants of a patient’s risk of cardiovascular disease.
But a growing number of doctors and researchers say it’s time to move beyond the current emphasis on “good” or “bad” cholesterol.
Instead, there is a potentially more accurate marker of heart attack risk: apolipoprotein B (“apoB” for short).
A better cholesterol test
Research shows that heart risk depends on the amount and type of cholesterol particles in the blood, and not so much on the cholesterol itself. ApoB is the particle that actually transports cholesterol into the circulation.
Decades of evidence show that measuring the number of ApoB particles in the blood predicts cardiovascular risk more accurately than the standard good cholesterol/bad cholesterol lipid panel, but cholesterol guidelines barely acknowledge the existence of current guidelines offer it. as an option only for certain high-risk patients.
As a result, most patients and even many doctors don’t realize that a better cholesterol test exists. “Old habits are hard to break,” says Ann Marie Nauer, MD, a cardiologist at UT Southwestern Medical Center in Dallas.
A standard cholesterol panel calculates the total amount or concentration of “bad” cholesterol, or LDL, in the blood, in milligrams per deciliter (technically, LDL-C). Since cholesterol is a fatty substance and therefore insoluble in water, it must be transported in small particles known as lipoproteins.
Testing for ApoB, a protein on the outside of LDL-carrying particles, counts the amount of these lipoprotein particles in the blood. In addition to LDL, it also captures other types of cholesterol such as IDL (intermediate density lipoproteins) and VLDL (very low density lipoproteins), which transport triglycerides.
Why is this important? As our understanding of heart disease improves, scientists recognize that apoB particles are more likely to clog the arterial wall, causing it to thicken and ultimately form atherosclerotic plaques. Therefore, the total number of APOB particles is more important than the total amount of cholesterol they carry.
In most people, apoB and LDL-C track fairly closely, says Dr. Alan Snyderman, a professor of cardiology at McGill University in Montreal. But some people have a “normal” amount of LDL-C but a high concentration of apoB particles, a condition known as “mismatch,” meaning they are at higher risk. But traditional cholesterol panels do not detect these patients.
“Two people can have exactly the same amount of cholesterol and a very different number of particles in the arterial wall,” says Snyderman, who has been researching APOB for decades.
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