ApoB Test May Be More Accurate Measure of Heart Disease Risk

Various cholesterol particles are associated with heart disease risk, including low-density lipoproteins (LDL), very low-density lipoproteins (VLDL), and intermediate-density lipoproteins (IDL). LDL-C specifically measures the weight of cholesterol within LDL particles and is commonly used to assess cholesterol risk. Each LDL, VLDL, and IDL particle contains a single protein on its surface known as apolipoprotein B (apoB). Previous research has demonstrated that the quantity of these "bad" cholesterol particles, which can be quantified through a blood test for apoB, serves as the most precise indicator of cholesterol risk. Current health guidelines, however, do not universally recommend apoB testing; typically, only LDL-C levels are measured, which do not account for the total number of LDL particles. Now, a new study reveals that standard lipid panels might not fully capture the risk of cholesterol-related heart disease. According to the findings published in JAMA Cardiology, measuring only LDL-C may fail to identify individuals with elevated levels of apoB.

Since cholesterol particle weight can differ from one individual to another, measurements of LDL-C and apoB do not always correlate. Discrepancies between apoB levels and LDL-C estimates are referred to as "discordant." Situations where individuals exhibit low or seemingly normal LDL-C levels but have high apoB levels can provide a false sense of security. This is more frequent among individuals with metabolic risk factors like obesity, diabetes, or high triglycerides. However, discordance can also occur in metabolically healthy individuals. In the study led by UT Southwestern Medical Center (Dallas, TX, USA), researchers analyzed data from the National Health and Nutrition Examination Survey (NHANES) encompassing 12,688 adults from 2005 to 2016, which included their apoB, LDL-C, high-density lipoprotein cholesterol (HDL-C, or “good” cholesterol), total cholesterol, and triglyceride levels.

To determine discordance for each participant, researchers computed the variance between the actual and expected apoB levels based on LDL-C. Not surprisingly, apoB levels in participants with metabolic risks were typically higher than anticipated. Nonetheless, even some metabolically healthy individuals had significant deviations in apoB from what was predicted. By adhering strictly to U.S. guidelines, physicians might overlook individuals who are at an elevated risk of developing atherosclerosis despite having normal metabolic health markers. The study introduces an online calculator allowing the public to estimate their apoB levels from their LDL-C scores. A higher-than-expected apoB level suggests a risk of heart disease is greater than what can be calculated using LDL-C alone.

“For most patients, the LDL-C measurement is usually ‘good enough’ because people with high LDL-C also usually have high apoB and vice versa, but that’s not true for everyone,” said senior author Ann Marie Navar, M.D., Ph.D., Associate Professor of Internal Medicine in the Division of Cardiology and in the Peter O’Donnell Jr. School of Public Health at UT Southwestern. “Some people have high apoB but a relatively low LDL-C, so their heart disease risk is underestimated by not measuring apoB. Others may have a high LDL-C but a low or normal apoB, and they aren’t at risk. I believe that our results, combined with a lot of other data showing the value of measuring apoB levels, support a revision of the guidelines to recommend apoB testing for everybody, not just those with certain clinical risk factors.”

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