Understanding Apolipoprotein B: A Potential Marker for Heart Disease Risk

Low-Density Lipoprotein (LDL), often labeled as ‘bad’ cholesterol, is a recognized risk factor for heart disease. Many individuals are screened for LDL levels during their annual health checkups. However, recent research suggests there is another blood marker that may more accurately predict heart disease risk: Apolipoprotein B (apoB). Despite its potential significance, apoB is not included in standard blood tests.

Apolipoprotein B is a protein attached to harmful fat particles in the bloodstream. It resides on the surface of lipoproteins such as LDL, known for contributing to heart disease. Each harmful particle contains a single apoB molecule, so measuring apoB levels effectively indicates the total number of plaque-forming compounds in the blood.

Traditionally, doctors focus on monitoring LDL levels to assess the risk of developing heart disease. High LDL levels may lead to recommendations for lifestyle modifications or medication aimed at reducing cholesterol.

Understanding Cholesterol and Lipoproteins

Cholesterol is a waxy, fat-like substance that plays a critical role in building cells and producing hormones, such as testosterone and estrogen. A lipid panel blood test typically provides information about total cholesterol levels, including LDL, very-low-density lipoprotein (VLDL), and high-density lipoprotein (HDL). The test also measures triglycerides, another blood fat linked to heart disease.

LDL and VLDL can accumulate in artery walls, leading to vessel narrowing and potentially causing heart disease, as explained by Dr. Ann Marie Navar, a preventive cardiologist at UT Southwestern Medical Center in Dallas. “Cholesterol isn’t dissolved in the blood like sugar and sweet tea. It’s packaged up in these things called lipoproteins,” said Navar.

ApoB vs. LDL: The Discordance

One issue with focusing solely on LDL levels is that normal LDL readings don’t necessarily equate to low heart disease risk. Some individuals may experience elevated apoB levels despite having normal LDL levels, a condition known as discordance. Factors like excess weight, diabetes, or high triglyceride levels can contribute to this discrepancy.

Although current guidelines from the American Heart Association do not advocate routine apoB screening during cholesterol tests, they do recommend it for certain patients with high triglycerides. Nonetheless, Dr. Navar believes all adults should undergo apoB screening, a practice she consistently applies to her patients.

Dr. Samia Mora from Brigham and Women’s Hospital suggests apoB testing at least once to compare with LDL results. Heart disease remains the leading cause of death for American men and women, and evaluating apoB may offer an important insight.

Apolipoprotein B Testing: How and Why?

Dr. Thomas Dayspring, a National Lipid Association fellow, emphasizes the value of apoB testing for assessing cardiovascular risk. He refers to the apoB test as the most reliable measure during risk assessments, as it evaluates artery-clogging particles directly.

An apoB test measures the number of harmful particles in the blood—distinct from LDL tests that quantify cholesterol carried by LDL particles. Dr. Jeffrey Berger from NYU Langone describes apoB as a comprehensive method to assess cholesterol burden and its role in plaque formation. Despite its potential benefits, it is estimated that under 1% of U.S. adults have undergone apoB testing, according to a 2024 study sponsored by Regeneron.

The popularity of apoB testing is growing, particularly among health influencers and in commercial blood testing markets. Recently, Sweetgreen, a salad chain, collaborated with Function Health to promote apoB screening alongside its products.

Dr. Michael Shapiro, chair of the American Heart Association’s Council on Lipidology, suggests using apoB testing selectively, especially in patients undergoing lipid-lowering therapies. When insurance does not cover the test, it typically costs about $70 at a laboratory.

Target ApoB Levels and Screening Rates

There is no universally accepted target for apoB levels. Generally, under 90 mg/dL is deemed acceptable for healthy individuals, with some researchers advocating lower levels around 70 mg/dL for optimal heart disease prevention.

Dr. Navar highlights a broader concern: many people aren’t getting their cholesterol checked regularly. Research from Johns Hopkins University reveals that nearly 25% of eligible adults haven’t been screened in the last five years, underscoring the importance of routine monitoring for heart health.

Dr. Akshay Syal, an internal medicine physician at UCLA Health and a member of the NBC News Health Unit, contributes to health reporting both digitally and on air for NBC News.