What is the clinical utility of Apolipoprotein B (ApoB) laboratory test?

From the Guidelines

Apolipoprotein B (ApoB) testing should be used as a valuable tool for assessing cardiovascular risk, with optimal targets of <80 mg/dL for high-risk patients and <100 mg/dL for those at high total CV risk, as recommended by the ESC/EAS Guidelines 1 and supported by other studies 1. To use ApoB testing effectively, it should be requested as part of a lipid assessment, especially in patients with a family history of heart disease, diabetes, metabolic syndrome, or if standard lipid panels show normal LDL but elevated triglycerides. Some key points to consider when using ApoB testing include:

• ApoB measures the total number of atherogenic particles in the bloodstream, making it superior to LDL-C measurement which only estimates cholesterol content.
• ApoB should be measured in a fasting state for the most accurate results, though non-fasting samples can still provide useful information.
• If ApoB is elevated, treatment typically involves lifestyle modifications (diet rich in fruits, vegetables, whole grains, regular exercise) and possibly medications like statins, ezetimibe, or PCSK9 inhibitors.
• Regular monitoring every 6-12 months is recommended for those on lipid-lowering therapy, with more frequent testing when adjusting treatment. The use of ApoB as a target for therapy is supported by studies showing its predictive value for cardiovascular risk reduction, with some studies suggesting it may be a better index of the adequacy of LDL-lowering therapy than LDL-C itself 1. However, it is essential to note that ApoB is not presently being measured in all clinical laboratories, and its use should be considered in the context of overall clinical judgment and patient risk assessment. In terms of specific treatment targets, the ESC/EAS Guidelines recommend ApoB targets of <80 mg/dL for subjects at very high CV risk and <100 mg/dL for those at high total CV risk 1, which is consistent with other studies 1. Overall, ApoB testing can be a valuable tool in assessing cardiovascular risk and guiding treatment decisions, particularly in high-risk patients.

From the FDA Drug Label

Rosuvastatin significantly reduced LDL-C (primary end point), total cholesterol and ApoB levels at each dose compared to placebo.

Table 13: Lipid-Modifying Effects of Rosuvastatin in Pediatric Patients 10 to 17 years of Age with HeFH ... ApoB 1Median percent change ... Table 14: Lipid-modifying Effects of Rosuvastatin in Pediatric Patients 7 to 15 years of Age with HoFH After 6 Weeks ... ApoB (mg/dL)268235-17.1% (-29.2, -2. 9)

The ApoB test is used to measure the level of ApoB in the blood.

• ApoB is a primary component of low-density lipoprotein (LDL), which is often referred to as "bad" cholesterol.
• The ApoB test can be used to assess the risk of cardiovascular disease.
• Rosuvastatin has been shown to significantly reduce ApoB levels in patients with heterozygous familial hypercholesterolemia (HeFH) and homozygous familial hypercholesterolemia (HoFH) 2.
• The ApoB test can be used to monitor the effectiveness of rosuvastatin treatment in reducing ApoB levels.
• However, the FDA drug label does not provide specific guidance on how to use the ApoB test.

From the Research

Using Lab Test ApoB

To use the lab test ApoB, consider the following points:

• ApoB represents the total concentration of atherogenic lipoprotein particles in the circulation and more accurately reflects the atherogenic burden of lipoproteins when compared to low-density lipoprotein cholesterol (LDL-C) 3, 4.
• ApoB is a validated clinical measurement that augments the information found in a standard lipoprotein lipid panel, and there is clinical value in using apoB in conjunction with a standard lipoprotein lipid profile when assessing risk and managing lipid-lowering therapy (LLT) 3.
• ApoB has been shown to be superior to LDL-C in risk assessment both before and during treatment with LLT 3, 4.
• When there is discordance between LDL-C and apoB, or LDL-C and non-HDL-C, atherosclerotic cardiovascular disease risk generally aligns better with apoB or non-HDL-C 3, 5.

Interpreting ApoB Results

When interpreting ApoB results, consider the following:

• The apoB target of <90 mg/dl is roughly equivalent to an LDL-C level <100 mg/dl and a non-HDL-C level <130 mg/dl in untreated patients 5.
• During statin therapy, to reach an apoB target of <90 mg/dl, it may be necessary to reduce non-HDL-C to <100 mg/dl or to reduce LDL-C to <70 mg/dl (in high-triglyceride patients) or <80 mg/dl (in lower-triglyceride patients) 5.
• Non-HDL-C may be an acceptable surrogate for direct apoB measurement, especially during statin therapy, due to the tight correlation between non-HDL-C and apoB 5.

Clinical Utility of ApoB

The clinical utility of ApoB is supported by the following points:

• ApoB is a more accurate marker of cardiovascular risk than LDL-C or non-HDL-C, and it can be measured accurately and precisely than LDL-C or non-HDL-C 4, 6.
• Adding apoB to a lipid panel would have only a trivial effect on costs, and no informed patient or physician would choose a less accurate test over a more accurate test if the more accurate test added only trivially to the total cost of care 6.