Doctors Say This Frequently Missed Test May Better Clarify Your Heart Disease Risk

What cholesterol tests may miss

If your doctor tells you your cholesterol is in a good range, it is easy to leave the appointment feeling reassured. The bloodwork is done, the numbers are reviewed, and you may think you have one less health worry to carry. But there is another marker that can raise the risk of heart disease and stroke, and a standard cholesterol panel does not measure it.

That marker is lipoprotein(a), or Lp(a). Its level is largely inherited, and diet and exercise usually do little to lower it. So even if you eat well, stay active, and have other cholesterol values that look fine, your Lp(a) may still be high.

It is more common than many people realize: about 1 in 5 people worldwide have elevated Lp(a), according to the American Heart Association (AHA).

For that reason, updated cholesterol guidelines from the American College of Cardiology, the American Heart Association and other medical groups recommend checking Lp(a) at least once in adulthood. The key point is that this is a separate blood test, so having your cholesterol checked does not necessarily mean this number has already been measured.

Cardiologists explain what the test can reveal and what usually happens if the result is elevated.

What is Lp(a)?

Cholesterol moves through the bloodstream inside particles known as lipoproteins. Lp(a), pronounced “L-P-little-a,” resembles an LDL particle but has an extra protein attached, says Archna Bajaj, M.D., a lipid disorders specialist at Penn Medicine and associate professor of clinical medicine at the University of Pennsylvania.

Like LDL, Lp(a) can contribute to plaque buildup in the arteries, which increases the risk of heart attack and stroke. Higher levels are also associated with aortic stenosis, a condition in which the valve that allows blood to leave the heart becomes narrowed.

You cannot infer your Lp(a) level from the rest of your cholesterol results alone, Dr. Bajaj says. She recently saw a woman in her late 40s who had no known medical conditions and was taking no medications. Her LDL cholesterol was 110 mg/dL, but her father had suffered his first heart attack at age 50. The patient wanted to know whether her own risk was greater than her routine labs suggested, so Dr. Bajaj ordered an Lp(a) test.

The result was more than 300 nmol/L, roughly four times the test’s upper limit of normal, which is below 75 nmol/L. “While she was initially hesitant on starting any medication, after I explained the risk associated with very high Lp(a) levels and that it likely explained her father’s early heart disease, she agreed to start a statin to lower her LDL-cholesterol and reduce her risk for having heart disease in the future,” Dr. Bajaj adds.

Who should have Lp(a) measured?

Adults who have never had this test should bring it up at their next medical visit, even if their cholesterol has always looked good. Current guidance recommends testing every adult at least once, and it becomes especially important if elevated Lp(a) runs in the family or there is a history of premature heart disease, before age 55 in men or 65 in women.

Dr. Bajaj says a simple blood test is all that is needed, and a primary care doctor can order it. Although Lp(a) is mostly inherited, genetic testing is not required to measure it.

You do not need to fast before the test, though it is worth checking whether any other bloodwork you are having done requires fasting. Before going to the lab, it is also smart to confirm whether insurance covers the test and whether there will be any out-of-pocket cost.

How to interpret a high result

Before focusing on the number itself, check the unit listed next to it. Lp(a) is reported either in nanomoles per liter (nmol/L) or milligrams per deciliter (mg/dL), and the same number can mean something different depending on the unit used.

The National Lipid Association uses the following categories:

• Lower risk: Below 75 nmol/L or below 30 mg/dL.
• Intermediate risk: 75 to below 125 nmol/L or 30 to below 50 mg/dL.
• Higher risk: 125 nmol/L or higher, or 50 mg/dL or higher.

It is best to use the unit on your lab report rather than trying to convert the result yourself, because there is no single reliable conversion formula, Dr. Bajaj explains.

Even if a report says “higher risk,” that does not mean Lp(a) alone can predict whether you will have a heart attack. Doctors use it alongside other factors such as age, other cholesterol values, blood pressure, medical and family history, smoking status and diabetes to estimate overall risk.

What to do if Lp(a) is elevated

“I tell patients that elevated Lp(a) is largely inherited, so it is not a reflection of poor lifestyle choices or something they did wrong,” says Dr. Bajaj.

Healthy habits still matter, even though they may not change this particular number very much. Eating well and exercising can improve blood pressure and blood sugar, which helps lower overall heart risk.

Your doctor may still recommend medication. Statins do not directly lower Lp(a), but they do reduce LDL cholesterol and help prevent heart attacks and strokes, says Cheng-Han Chen, M.D., board-certified interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in Laguna Hills, California.

Daniel E. Soffer, M.D., an internist, clinical lipidologist and associate professor of medicine at the University of Pennsylvania, says the decision depends on your overall risk profile and how aggressively LDL should be lowered. A person who already has heart disease may need a stronger treatment plan than someone with fewer other risk factors.

There are treatments being studied that specifically target Lp(a), but none is approved for that purpose right now. Lipoprotein apheresis, which filters Lp(a) and LDL from the blood, is reserved for a small group of patients who meet specific criteria, including certain inherited cholesterol disorders and artery disease, Dr. Soffer says. Most people will not need it.

Do you need a cardiologist?

Not always. Your primary care doctor can explain the result and help determine next steps. If your Lp(a) is very high, heart disease runs early in your family, or your overall risk is difficult to assess, a cardiologist or lipid specialist may be helpful.

In some situations, doctors may also discuss a coronary artery calcium scan, which looks for calcified plaque in the arteries that supply the heart. Yu-Ming Ni, M.D., board-certified cardiologist and lipidologist at MemorialCare Heart and Vascular Institute at Orange Coast Medical Center in Fountain Valley, California, says he uses the scan to help guide medication decisions when the risk picture is unclear.

If you have had preeclampsia or gestational diabetes, make sure your doctor knows, even if the pregnancy was years ago. “That history still matters when assessing your heart health,” says Tala K. Al-Talib, M.D., a cardiologist and medical director of cardiology at Johns Hopkins Greenspring Station.

Should relatives be checked too?

If your Lp(a) is high, let your siblings, parents and adult children know, Dr. Bajaj recommends. Because elevated levels often run in families, your result may prompt them to get tested and uncover a risk factor they might otherwise miss.

For younger children, start with a pediatrician. The National Lipid Association recommends testing certain children, including those with a parent or sibling who has elevated Lp(a), rather than screening every child routinely.

The takeaway

If you have never had Lp(a) checked, it is worth asking at your next appointment: “Have I ever had my Lp(a) checked, and if it is high, how would that change my prevention plan?”

Dr. Bajaj adds that pregnancy, menopause and certain conditions such as kidney or thyroid disease can affect the level, so your doctor should know about your overall health when deciding when to test and whether repeat testing is needed. You may only need the test once, but you should understand what the result means and what steps can help protect your heart.

Learning that your Lp(a) is high can be unsettling, especially if you have been doing your best to stay healthy. Even so, the result can give your doctor useful information for managing your other heart risk factors.