Apolipoprotein B 

Updated: Nov 21, 2014
  • Author: Georges Elhomsy, MD, ECNU, FACE; Chief Editor: Eric B Staros, MD  more...
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Reference Range

Apolipoprotein B (apoB) levels are used to evaluate the risk for cardiovascular disease.

The reference range of apoB levels in adults is less than 130 mg/dL (1.3 g/L).

ApoB levels are higher in males than in females and tend to increase with age.

It has been suggested the range be adjusted according to the risk factor stratification, [1] similar to LDL cholesterol (LDL-C).

Table 1. Reference Ranges of ApoB levels Relative to LDL-C levels (Open Table in a new window)

Risk ApoB LDL-C
High risk: CHD or CHD risk equivalent < 90 mg/dL < 100 mg/dL
Moderate risk: ≥2 risk factors < 110 mg/dL < 130 mg/dL
Low risk: 0-1 risk factors < 130 mg/dL < 160 mg/dL
CHD, coronary heart disease

 

Table 2. ADA/ACC Consensus Report Treatment Goals in Patients with Cardiometabolic Risk and Lipoprotein Abnormalities [2] (Open Table in a new window)

Risk ApoB LDL-C Non-HDL-C
Highest-risk patients: Known CVD or DM plus ≥1 additional major CVD risk factor < 80 mg/dL < 70 mg/dL < 100 mg/dL
High-risk patients: ≥2 CVD risk factors but no DM or known CVD or DM but no other major risk factors < 90 mg/dL < 100 mg/dL < 130 mg/dL
CVD, cardiovascular disease; DM, diabetes mellitus
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Interpretation

Elevated apolipoprotein B (apoB) levels indicate an increased risk of cardiovascular disease. [3, 4, 5, 6]

ApoB levels may be increased during pregnancy or coffee consumption, as well as during the fall and winter seasons.

Low apoB levels may indicate Bassen-Kornzweig syndrome (abetalipoproteinemia), a very rare genetic condition characterized by apolipoprotein B deficiency.

Other conditions that are associated with low apoB levels include the following:

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Collection and Panels

Specimen type: Plasma EDTA

Patient instruction: Overnight fasting (12-14 hours)

Collection tube: Lavender top (EDTA)

Unacceptable conditions: Hemolyzed specimens

Specimen preparation: Separate serum from cells as soon as possible or within 2 hours of collection and transfer 1 mL serum to transport tube

Storage/transport temperature: Refrigerated

Stability: Refrigerated 8 days; frozen 3 months

Panels: None

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Background

Description

Apolipoprotein B (apoB) is a structural protein that constitutes a major component of the very-low-density lipoprotein (VLDL), the intermediate-density lipoprotein (IDL), and the low-density lipoprotein (LDL). Each of these lipoprotein particles carries one apoB molecule; as a result, the total serum apoB level corresponds to the total number of VLDL, IDL, and LDL particles.

Because VLDL, IDL, and LDL are considered atherogenic, the apoB level should reflect the atherogenic potential of these lipoproteins.

Cardiovascular risk is associated more with the number and size of circulating atherogenic particles than with the concentration of cholesterol in these particles. ApoB is not equivalent to non-LDL-C, because the latter reflects the cholesterol content of all atherogenic lipoproteins rather than the total number of circulating atherogenic particles.

ApoB plays a central role in carrying cholesterol and triglycerides from the liver and gut to utilization and storage sites.

Indications/Applications

Incontestable data support the concept that apoB is a better tool to assess cardiovascular disease than LDL-C and non-DHL-C.

Furthermore, apoB seems to be a very important parameter in assessing cardiovascular risk in the setting of diabetes and metabolic syndrome, since patients with these conditions tend to have small, dense LDL particles with relatively normal LDL-C but high apoB levels.

In addition, several clinical trials have shown that apoB is a better marker for monitoring patients on statin therapy for residual risk than LDL-C.

Finally, a Consensus Conference Report by the ADA/ACC has recommended the use of apoB level for risk assessment in persons at high risk for cardiometabolic disease.

Considerations

Familial hypercholesterolemia is a rare disease caused by a mutation in the apoB gene code. Patients with the homozygous mutation tend to develop cardiovascular disease in childhood.

Overnight fasting might not be necessary to evaluate apoB levels, but most laboratories recommend it.

Some evidence has shown that the capacity of the apoB/apoA-I ratio in assessing cardiovascular risk is strong and may be better than the use of apolipoprotein B alone.

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