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ApoB tests can help doctors evaluate cholesterol levels and, in some cases, provide a better understanding of a person’s risk for heart disease and stroke than a standard lipid panel. Klaus Vedfelt/Getty Images
      • An ApoB cholesterol test can help identify your risk for heart disease.
      • The test is not on standardized lipid panel testing that doctors typically perform at annual exams.
      • “Good” and “bad” cholesterol still matter for heart health, but understanding ApoB levels can give clinicians more information to work with.

      You’ve most likely heard of HDL (“good”) and LDL (“bad”) cholesterol.

      The U.S. Centers for Disease Control and Prevention (CDC) describes each as the following:

      • High-density lipoprotein (HDL) cholesterol can decrease the risk for heart disease and stroke because it carries cholesterol to the liver, which removes it from the body.
      • Low-density lipoprotein (LDL) cholesterol makes up most of the cholesterol in the body. Having high LDL cholesterol raises the risk for heart disease and stroke because it builds up as plaque on the walls of your blood vessels, which can lead to heart disease and stroke.

      HDL and LDL cholesterol are often measured based on a blood draw and standard lipid panel test taken during an annual exam at the doctor’s office. The panel also measures total cholesterol and triglycerides, a type of fat in the blood that can raise risks for heart disease and stroke.

      Doctors are mostly looking for “bad” cholesterol levels detected on the panel.

      However, did you know that Apolipoprotein B (ApoB) is the main protein found in LDL cholesterol and can be tested, too?

      “The LDL cholesterol value you get from the doctor is actually a calculated estimate of the concentration of LDL particles in the bloodstream, but the ApoB number is a direct measure of all the particles that could contribute to cardiovascular disease in your bloodstream,” Renee Deehan, PhD, vice president of science at InsideTracker, told Healthline.

      Dr. Salim Virani, a cardiologist at The Texas Heart Institute and the Aga Khan University, explained that cholesterol is carried in LDL, very-low-density lipoproteins (VLDL), intermediate-density lipoproteins (IDL), and lipoprotein(a) particles.

      Each of those particles has a protein attached to it and the protein is ApoB.

      ApoB protein moves fat throughout the body and helps it to get through the walls of arteries, where they form plaque. When this happens, it increases the risk of heart disease and stroke.

      “We still need to do a better job of explaining to patients what good cholesterol and bad cholesterol are. After that, if you have a patient who is very interested in knowing more about their risk of heart disease pertaining to cholesterol, then you can make the transition to the next level and get into explaining to them fully what ApoB particle concentration is and how it is different from the usual LDL cholesterol that we measure on a standard lipid panel,” Virani told Healthline.

      LDL cholesterol that is measured on a standardized lipid panel shows how much cholesterol is carried in a person’s LDL particles, and for the most part, is a good measure of cholesterol-associated risk, said Virani.

      However, tests for ApoB levels have been around for over a decade and are becoming more standardized in recent years, he said.

      “I think sometimes knowing ApoB is more important for clinicians who need information beyond just regular cholesterol that they measure with the lipid panel and there is a subset of patients where it might be more useful,” Virani said.

      For instance, he said patients who are obese, have high triglycerides, or who have metabolic syndrome (low HDL cholesterol and high triglycerides) may benefit from ApoB testing.

      “[In] those cases, LDL cholesterol — what we have traditionally measured — may not be the perfect marker in terms of letting a clinician and patient know what their risk is related to cholesterol, and in those cases, measuring ApoB could be helpful in deciding what kind of therapies to use on the patient,” Virani said.

      Dr. Deehan noted that ApoB should be a complement, rather than a replacement for HDL cholesterol, LDL cholesterol, and non-HDL cholesterol values.

      “They have been studied for decades, and there is a large body of knowledge linking them to disease risk that is valuable context to have. Plus, clinicians have been working with these numbers for decades, and are comfortable with them,” she said.

      Moreover, some providers might prefer to calculate ApoB levels on their own without an additional test, said Virani. They do this by looking at the lipid panel results and calculating the non-HDL cholesterol number by subtracting good cholesterol from total cholesterol. Whatever number is left signifies the value for overall bad cholesterol.

      “That number you get out of that (known as non-HDL cholesterol) is very highly correlated with ApoB; about 90% or more in most cases, so don’t be surprised if you ask your clinician to test ApoB and your clinician says, ‘I understand what non-HDL cholesterol is. It’s very highly correlated with ApoB so we may not need to measure ApoB directly because it’s an extra test and non-HDL cholesterol I can get from any standard lipid panel,’” he said.

      However, some doctors are not comfortable using the calculation to guide how they treat a patient, Virani noted. In these cases, they may prefer to use an ApoB test.

      Deehan added that while ApoB and LDL values are often highly correlated, discordance is possible. For example, she explained that moderately elevated levels of LDL and elevated ApoB levels may cause concern compared to someone with the same elevated LDL but optimal levels of ApoB.

      “There is evidence that cardiovascular risk better follows your ApoB levels than other common lipid metrics,” she said. “This additional context matters, and allows clinicians and researchers to better understand the contributors to cardiac disease risk in a more refined way.”

      When high ApoB levels are detected, the initial first steps for treatment are the same as they would be for detection of high LDL levels; dietary changes, such as eating foods low in saturated and trans fats, and maintaining a healthy weight through diet and exercise. LDL-lowering medications, such as statin therapy, are also often prescribed, said Virani.

      Because cholesterol can be carried by VLDL particles, which have high triglycerides, he said finding ways to treat triglycerides might also be part of the treatment plan.

      “Most of the ApoB is carried in traditional LDL particles, but in addition, it can be carried by other particles high in triglycerides as well, which are not good for the heart. Knowing what we know about heart disease and cholesterol, you will always treat LDL cholesterol first and then go to other lipid parameters that may also explain why ApoB is high,” said Virani.

      ApoB measurement is a valid way for doctors to evaluate cholesterol levels and in some cases may provide a better understanding of a person’s risk for heart disease and stroke than a standard lipid panel.

      However, a ApoB test is not necessary for everyone. Talk to your doctor about whether it makes sense for you.