The blood tests that can flag your hidden heart disease risk

The first measures a protein called apolipoprotein B, or apoB for short, that contributes to artery-blocking plaque. The other test, for lipoprotein(a), measures a type of bad cholesterol.

High levels of each have been linked to increased risk of heart disease.

A growing number of specialists and primary care doctors say these tests can help give you a more precise and earlier indication of possible heart problems than more common tests for things like LDL, the best-known bad cholesterol marker. In some cases, these lesser-known tests identify at-risk people whose standard lipid tests look normal.

Proponents say the tests should supplement, not replace, your standard lipid panel, which is generally recommended every one to six years for adults.

Other doctors are wary of ordering the tests, citing a lack of consensus on what constitutes normal levels and whether and how to treat them—not to mention the extra cost. U.S. medical organization guidelines don’t universally recommend them.

How these tests could help

A growing body of research on apoB suggests it is a better predictor of heart disease risk than the better-known LDL cholesterol.

Up to 20% of patients with normal LDL cholesterol levels will have high levels of apoB, says Dr. Marc Penn, a cardiologist and a medical director at laboratory testing company Quest Diagnostics.

“You’re actually getting a much better assessment of the number of particles that are carrying cholesterol in the blood that could potentially lead to atherosclerosis" when measuring apoB, says Dr. Shriram Nallamshetty, a preventive cardiologist at the Palo Alto VA Medical Center.

Similarly, high lp(a) levels, which are thought to start between 30 and 50 mg/dL and affect roughly 20% to 30% of people, have been linked to increased risk for heart attack, stroke and other cardiovascular diseases.

You can lower your apoB levels by taking certain drugs, like statins, and through dietary changes, such as limiting saturated fats.

Your lp(a), by contrast, is genetic and doesn’t change much over the course of your life. But if tests show high levels, you can lower your heart-disease risk in other ways, such as with medication or changes to diet and exercise.

Buddy Touchinsky, a chiropractor who runs an integrative medicine practice in Pennsylvania, decided last year to start running both tests on every patient. Last year, Touchinsky’s own lp(a) test revealed a level significantly above the high-risk threshold.

“If I would have started more aggressively treating this 20 years ago, maybe I wouldn’t have any plaquing in my arteries at all," says Touchinsky.

Touchinsky was able to bring down his apoB level by reducing his consumption of foods like red meat, butter and full-fat dairy, upping his exercise and taking a low-dose statin, as well as another cholesterol-lowering drug called ezetimibe.

Who should get them

Doctors disagree about who should get these tests.

“Some people are doing everything they can to be healthy already and have a lot of anxiety," says Dr. Nalin Dayawansa, a research and interventional cardiology fellow at the Alfred Hospital in Melbourne, Australia. “A lot of that information is just noise and wasted money if it doesn’t directly influence what you do."

The American College of Cardiology and the American Heart Association don’t recommend them for everyone. Instead, they recommend lp(a) testing for adults with a family history of premature heart disease, or if you have atherosclerotic cardiovascular disease that isn’t explained by common risk factors like smoking.

These groups say that measuring apoB may have advantages for some people, especially if you have high levels of triglycerides, or fat, in the blood.

People with signs of insulin resistance and abdominal obesity are also likely to benefit from apoB testing, says Dr. Daniel E. Soffer, an internist and lipidologist at the University of Pennsylvania and past president of the National Lipid Association. He estimates that, combined with those with high triglyceride levels, these groups account for roughly 40% to 50% of the U.S. adult population.

Some major European medical organizations recommend every adult have their lp(a) levels measured at least once. In the U.S., the National Lipid Association, which represents lipid-disorder specialists, adopted the same recommendation in March this year.

Children, too, can benefit from an lp(a) test, particularly if one or both parents had a heart attack or other cardiovascular event at a young age, says Dr. Christie Ballantyne, president of the National Lipid Association and professor of medicine at Baylor College of Medicine.

“Atherosclerosis is more reversible early in life," says Ballantyne.

Gaining traction

Testing companies including Labcorp and Quest have started offering consumer-initiated and at-home tests for patients who don’t want the hassle of asking their doctors to order them.

Lp(a) and apoB testing are generally not covered by insurance, and out-of-pocket costs range from roughly $25 to $150.

Jennifer Mannino says she wishes lp(a) had been part of standard preventive care before her husband went into cardiac arrest at age 48 in 2020. Complications left him struggling with short-term memory and executive functioning.

After the cardiac arrest, he had an lp(a) test, which was high. A standard lipid test taken in the year prior had revealed levels classified near optimal. He added a new medication to the statin he was already taking, and his LDL cholesterol levels have dropped significantly.

“Once you have one more piece of information, it creates better conversations with your doctor," says Mannino.

Write to Alex Janin at alex.janin@wsj.com