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3 Cholesterol Tests to Consider
A blood panel can tell you if your cholesterol is high, but it doesn’t always show the full picture of your heart risk
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High cholesterol is often touted as an indicator of poor heart health — as the numbers climb, so does your risk of a heart attack or stroke. This is especially true if what’s elevated in your bloodstream is low-density lipoprotein (LDL) cholesterol, often called “bad” cholesterol.
A routine blood test can flag high LDL levels, but cardiologists say these values alone don’t always tell the full story of your heart health — and that several other tests can offer a clearer picture of your risk.
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Here’s a look at three of these tests, and advice from experts on who might need them.
Understanding cholesterol
What is cholesterol, exactly? It’s a waxy, fat-like substance made by the liver. Despite its bad reputation, your body needs cholesterol to carry out several essential functions, like making hormones, building cells and aiding digestion. Too much of it, however, can clog your arteries, increasing the risk of a heart attack or stroke.
Because cholesterol is a fat-like substance, like an oil — “and oil and water do not mix,” says Dr. Allan Sniderman, a cardiologist at McGill University in Montreal — it moves through the blood on a protein called a lipoprotein. LDL is one type of lipoprotein in the body; there’s also high-density lipoprotein (HDL), sometimes referred to as “good” cholesterol, since it helps to flush cholesterol from the body.
One key difference between LDL and HDL is a protein known as Apolipoprotein B (ApoB), which is only found on the surface of LDL and other potentially artery-clogging particles.
1. ApoB test
For decades, standard cholesterol tests (lipid panels) have estimated LDL cholesterol levels by essentially measuring the cholesterol carried within lipoproteins.
The problem with this, Sniderman says, is that while this type of blood test can approximate the amount of LDL cholesterol circulating in your blood, it does not reveal the number of LDL particles that can stick to artery walls and increase the risk of heart disease.
An ApoB test, on the other hand, estimates how many LDL particles are actually shuttling that cholesterol around and contributing to plaque buildup.
Dr. Michael Shapiro, a professor of cardiovascular medicine at Wake Forest University School of Medicine,
likens the difference to counting passengers versus cars on a road: A standard cholesterol panel measures the passengers, Shapiro explains on the American Heart Association's website, while an ApoB test measures the cars that can clog the roadways. So, by focusing on ApoB, “what we actually measure clinically is the total number of bad particles,” Sniderman says.
A study published in JAMA by Sniderman and colleagues in April shows that testing for ApoB is more cost-effective for the U.S. health care system compared to LDL and non-HDL, since reaching an ideal ApoB level led to the highest reduction in cardiac events.
Though an ApoB blood test may cost more than the standard lipid panel, there’s “a large increase in quality-adjusted life years by reducing risk of heart attacks and reducing risks of strokes,” study coauthor Ciaran Kohli-Lynch says.
New cholesterol guidelines recommend ApoB testing for people who are on lipid-lowering therapy, as well as those with existing heart disease, diabetes or high triglyceride levels (≥150 mg/dL).
According to the Cleveland Clinic, the normal range for ApoB is 66-133 mg/dL in men and 60-117 mg/dL in women. A reading that is higher than 130 mg/dL indicates you’re at higher risk of cardiovascular disease.
2. Lipoprotein(a) test
The latest cholesterol guidelines recommend that everyone test for the presence of another lipoprotein called lipoprotein(a) or Lp(a), at least once in their lifetime.
This lipoprotein is very similar to LDL, explains Dr. Harpreet Bhatia, a cardiologist at UC San Diego Health. Only, it has an extra protein that makes it more likely than LDL to cause plaque buildup in the arteries, the American Heart Association says.
Another thing that makes it different from LDL “is that it’s almost entirely genetic,” Bhatia says. Because it’s hereditary, diet, exercise and other lifestyle behaviors that often impact the levels of other lipoproteins have little to no effect on Lp(a). Meaning, your diet and exercise routine could be near perfect, and you could still have high cholesterol.
About 1 in 5 adults has an elevated Lp(a) level, yet less than 1 percent of U.S. adults have tested for it.
Dr. Brian Downey, director of general cardiology services at Tufts Medical Center in Boston, says someone’s Lp(a) could inform a person’s risk beyond what would normally be predicted from just using the standard lipid markers.
High Lp(a) — which is 125 nmol/L or greater or 50 mg/dL or greater — is associated with about a 1.4-fold increased long-term risk of heart attack or stroke, according to the American Heart Association. A reading of 250 nmol/L is associated with at least a two-fold increased long-term risk of heart attack or stroke.
3. Coronary artery calcium (CAC) test
While Lp(a) and ApoB tell a person’s risk of developing heart disease, a coronary artery calcium (CAC) test can show what the disease currently looks like.
It’s a CAT scan of the heart arteries, Bhatia says.
“The calcium itself isn’t necessarily the problem; it’s more that the calcium represents underlying cholesterol. When cholesterol deposits in the coronary arteries over time, calcium can become incorporated in those arteries, and we can see it with a CAT scan,” Bhatia explains.
A higher score indicates more plaque buildup in the arteries. For example, a score of 0 means your risk of coronary artery disease is likely low; a score between 100 and 299 indicates moderate risk; and a score of 300 or higher suggests a significant amount of plaque is present and your risk of coronary artery disease is severe, according to the American Heart Association. Even if your score is low, however, it does not mean that all risks of atherosclerosis (the hardening of your arteries from plaque buildup) are ruled out. That’s because CAC scoring cannot detect the presence of soft or uncalcified plaque in arteries, which can cause coronary artery disease.
People whose heart disease risk falls in a borderline or intermediate range may want to ask their doctor whether a CAC test could help clarify their risk and guide decisions about starting cholesterol-lowering medication, Bhatia says. The American Heart Association says CAC testing may also be useful for men 40 and older and women 45 and older when doctors need a better picture of their long-term risk of cardiovascular disease.
Everyone should get a cholesterol screening
Heart disease remains the top killer in the U.S.: It’s responsible for 1 out of every 5 deaths, the Centers for Disease Control and Prevention says.
“I think one message in general is that everyone should have all their cardiovascular risk factors assessed,” Bhatia says. Knowing your risk can help you and your doctor take steps to protect your heart over the long term, he adds.
When it comes to routine screening, Medicare covers standard lipid panels, but generally does not cover ApoB, Lp(a) or CAC scoring tests. Coverage by other medical insurance plans varies, with out-of-pocket costs for the blood tests ranging from $50 to $150. The cost of the imaging scan, without coverage, can be even higher.
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