A standard cholesterol panel reports total cholesterol, LDL, HDL and triglycerides. Those numbers still do most of the work in heart risk assessment. Two other tests, apolipoprotein B (ApoB) and lipoprotein(a), usually written Lp(a), can add useful detail for some people, and one of them is worth checking at least once in a lifetime.

The National Heart, Lung, and Blood Institute explains that high LDL cholesterol can build up in the walls of arteries and raise the risk of heart attack and stroke. Cholesterol travels in the blood inside particles called lipoproteins. LDL is one of them; there are others.

What ApoB measures

Each LDL particle, and each of several related particles that can lodge in artery walls, carries one molecule of apolipoprotein B. Measuring ApoB is a way of counting those potentially harmful particles, rather than measuring the cholesterol they carry.

Most of the time ApoB and LDL tell a similar story. They can diverge in people with high triglycerides, diabetes, insulin resistance or obesity, where LDL may look acceptable while the particle count is high. The 2018 cholesterol guideline from the American Heart Association and American College of Cardiology lists a high ApoB of 130 mg/dL or higher among its risk-enhancing factors, particularly when triglycerides are high.

What Lp(a) is

Lipoprotein(a) is an LDL-like particle with an extra protein attached. An American Heart Association scientific statement describes high Lp(a) as an independent and causal risk factor for heart attack and stroke, and notes that roughly 70 to over 90 percent of the variation in Lp(a) levels between people is genetically determined.

That has practical consequences:

  • It is common. The National Lipid Association estimates that about one in five people has a high Lp(a).
  • It is mostly inherited. Because levels are largely set by genes, a healthy diet and exercise, while valuable for other reasons, are not expected to change Lp(a) much.
  • It runs in families. The NLA notes that testing first-degree relatives of someone with a high level can identify others at risk.
  • It is not on a standard panel. It has to be ordered specifically.

Who should be tested

In a 2024 update, the National Lipid Association recommended measuring Lp(a) at least once in every adult for risk assessment. It considers levels below 75 nmol/L (30 mg/dL) low risk, 125 nmol/L (50 mg/dL) or higher high risk, and values in between intermediate. The 2018 guideline lists Lp(a) of 50 mg/dL or 125 nmol/L or higher as a risk-enhancing factor.

Testing is especially worth discussing if you or a close relative had a heart attack or stroke at a young age, if heart disease runs in the family despite normal cholesterol, or if you are deciding whether to start a statin and the decision is close.

What a high result means

A high Lp(a) does not mean a heart attack is coming. It means the rest of your risk factors deserve closer attention. The NLA recommends earlier, more intensive management of other risk factors for people with high Lp(a), including lifestyle changes and, for those at high risk, cholesterol-lowering medicine aimed mainly at LDL. The AHA statement notes that there are not yet treatments approved specifically to lower Lp(a) for heart protection, and research is ongoing; ask Dr. Shtern about the current state of the evidence.

A high Lp(a) or ApoB can also be one of the findings that makes a coronary artery calcium score worth considering. The Mediterranean diet and heart-healthy foods still help with LDL and overall risk, even if they do little for Lp(a).

Reading the result

Lp(a) results come in one of two units, nmol/L or mg/dL, depending on the lab. The two are not simply interchangeable, so compare a new result with an old one only when the units match. The AHA statement notes that Lp(a) tests are not yet fully standardized across labs, another reason to keep your results together in one place and have one doctor read them over time.

Because Lp(a) is mostly inherited, a single measurement is enough for most adults. ApoB, like LDL, can change with diet, weight and medicine, so it may be checked again if it is being used to guide treatment.

Asking for these tests

Both tests are simple blood draws. Ask your doctor whether they would add anything to your picture, and check with your insurance about coverage before the draw if cost is a concern.

At Legacy Medical, blood is drawn in the office and Dr. Shtern takes the time to explain what each number means for you, including how cholesterol, blood pressure and kidney function fit together. The annual executive physical is a natural time to ask. To meet her first, book a complimentary meet and greet.

This article is general information, not advice for your situation. Members can call the office with questions about their own care.