A new study from University of Texas Southwestern Medical Centre says that the standard lipid panel might not fully show the risk of heart disease linked to cholesterol. This means that many people across the world don't have a full picture of their health. The publication of the study in JAMA Cardiology underscores the criticality of low cost test for assessing the apolipoprotein B (apoB) levels, which could give a more true picture of heart disease risk than the usual LDL-C test.

Little bits of cholesterol called low-density lipoproteins (LDL), very low-density lipoproteins (VLDL), and intermediate-density lipoproteins (IDL) damage the heart. Most of the time, people check LDL-C, which figures out how much cholesterol is in LDL particles. Apolipoprotein B (apoB) is a protein that is on the surface of all LDL, VLDL, and IDL particles. A previous study has shown that an apoB test is the best way to find out how many of these "bad" cholesterol particles there are.

“The LDL-C measurement is usually ‘good enough' for most patients because people with high LDL-C also generally have high apoB and vice versa,” said Dr Ann Marie Navar, senior author of the study and Associate Professor of Internal Medicine at UT Southwestern. “But that's not always the case. If you don't measure apoB, you might not know that some people have a high chance of heart disease even though their LDL-C level is low. Some people may have a high LDL-C level but a normal or low apoB level, so they are not at risk."

The difference is due to the fact that cholesterol particles have different weights in different people, which can cause LDL-C and apoB levels to not match up correctly. These differences, known as "discordant" levels, are particularly concerning when LDL-C levels appear average but apoB levels are high. People with metabolic risk factors like obesity, diabetes, or high triglycerides may experience this discordance more often, but people without these diseases can also have it.

The study looked at apoB discordance in the U.S. population using data from the National Health and Nutrition Examination Survey (NHANES). The database, containing data from 12,688 individuals, demonstrated the frequency of apoB levels deviating from the expected levels based on LDL-C. As expected, apoB levels were higher than expected in people who had metabolic problems. Some people who had a healthy metabolism had apoB amounts that varied a lot, which was surprising.

Dr Navar believes that we need to change the current guidelines. He said, "I believe that our results, along with a lot of other data showing the value of measuring apoB levels, support a revision of the guidelines to recommend apoB testing for everyone, not just those with certain clinical risk factors."

The study also has an online calculator that people can use to get a rough idea of their apoB amounts by entering their LDL-C numbers. According to Dr. Navar, an apoB number that is higher than expected can indicate a risk of heart disease that LDL-C alone may not fully show.

Dr Eric Peterson,  Vice Provost and Senior Associate Dean for Clinical Research at UT Southwestern, contributed to this study. Dr. Peterson, who is also Professor of Internal Medicine and Vice President for Health System Research, holds the Adelyn and Edmund M. Hoffman Distinguished Chair in Medical Science.