ApoB testing may reveal patients at risk of heart disease missed by cholesterol tests: study

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Testing apolipoprotein B-100 (ApoB) levels may identify patients who have low LDL cholesterol (LDL-C) but may still be at elevated risk of cardiovascular disease, a retrospective study has found.

Physicians routinely test for LDL-C and HDL-cholesterol to assess if an individual is at risk of heart disease and requires treatment or management. However, some research suggests ApoB testing may give a more accurate picture of risk. ApoB carries fat molecules, including the risk factor LDL-C. As such, while testing for the protein will not directly check LDL-C, it will show the level of the particles that carry cholesterol.

“Data suggest that these particle numbers increase risk to a greater extent than just cholesterol levels alone,” Dr. Jeffrey L. Anderson, Intermountain Health cardiologist, said in a statement. “ApoB could help us identify a population of patients with normal or even low LDL numbers but who are at higher risk and should be more aggressively treated.”

Anderson served as principal investigator on a study designed to understand the size of the population that may benefit from ApoB testing. In the study, details of which were presented at the 2023 American College of Cardiology annual Scientific Sessions in New Orleans, investigators looked at Intermountain Healthcare electronic medical records for patients who had ApoB and standard lipid profiles tested within 90 days of each other from 2010 to early 2022.

The analysis showed that testing for ApoB has increased in recent years, rising from 29 cases in 2010 to 131 cases in 2021, but remains rare. Levels of ApoB positively correlated with LDL-C, reflecting the fact that the particles are used to carry cholesterol. More cholesterol means more ApoB particles.

However, the ratio of ApoB to LDL-C increased as levels of the cholesterol decreased. The Intermountain Health researchers interpreted the finding as evidence of “an excessive number of atherogenic small, dense LDL particles -- those particles with smaller amounts of LDL cholesterol per particle.”

Defining an ApoB level of below 60 mg/dL as optimal, the researchers found 46% of patients with LDL-C below 70 mg/dL had suboptimal levels of the protein. Adults with a history of atherosclerosis (narrowing of the arteries) are recommended to keep their LDL-C levels below 70 mg/dL. Increasing the threshold for optimal ApoB to 75 mg/dL reduced the proportion of patients with suboptimal levels to 14%.

The research suggests that ApoB could help identify patients with normal or even low LDL numbers who are at higher risk and should be more aggressively treated. ApoB testing is somewhat expensive and has yet to become part of routine care.

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