Apolipoprotein B (Apo-B)

Access Medical Labs offers the Apolipoprotein B test as an add-on test to a standard lipid panel when a targeted assessment of cardiovascular risk assessment is desired. It can be a useful addition to a standard lipid panel, especially in individuals with a personal or family history of high cholesterol, or for people who are not responding as expected to conventional diet, lifestyle, and medication therapies.

The Apolipoprotein B test is typically performed as part of a comprehensive lipid panel, which includes other lipid markers such as total cholesterol, HDL cholesterol, and triglycerides. This allows for a more comprehensive assessment of a patient's lipid profile and cardiovascular risk.

The interpretation of Apolipoprotein B levels should be done in conjunction with other clinical information and risk factors. Consider your patient's overall lipid profile, medical history, family history, and other relevant factors to determine the appropriate course of action based on the test results.

What is Apolipoprotein B?

Apolipoprotein B (ApoB) is a protein that plays a crucial role in lipid metabolism and transport. It is the primary protein component of atherogenic particles such as very low density lipoprotein (VLDL) particles, intermediate-density lipoprotein (IDL) particles, low-density lipoprotein (LDL) particles and lipoprotein a Lp(a) particles.  These particles are responsible for carrying cholesterol and triglycerides in the bloodstream and depositing them into cells and tissues. ApoB acts as a ligand for LDL receptors, allowing the uptake of LDL particles by cells that require cholesterol for various cellular processes.

There are two known forms of apoB: apoB100 and apoB48.  In humans, apoB100 is primarily synthesized in the liver, and apoB48 is primarily synthesized in the intestines.¹  ApoB100 is found on the surface of VLDL, IDL, LDL and Lp(a) particles; therefore, only ApoB100 particles are considered clinically relevant when assessing for cardiovascular disease risk.  An ApoB blood test only measures ApoB100 particles.²

ApoB is considered a more sensitive marker for cardiovascular disease risk than LDL alone because there is one ApoB molecule on the surface of every potentially atherogenic particle: VLDL, IDL, LDL, and Lp(a).  Therefore, an ApoB measurement provides a direct count of the total number of potentially atherogenic particles, while a standard lipid panel can only calculate the number of LDL particles present.³

Elevated levels of ApoB are associated with an increased risk of cardiovascular diseases as well as increased likelihood of insulin resistance.⁴ Measuring ApoB levels can provide valuable information about an individual's cholesterol metabolism and their risk of developing heart disease. It is often used in conjunction with other lipid markers including a complete lipid panel and occasionally sdLDL (small dense LDL particles, which are more atherogenic than larger LDL particles) to assess cardiovascular risk and guide treatment decisions.⁵

Who should get an Apolipoprotein B test?

Ideal candidates to be tested for Apolipoprotein B (ApoB) are individuals who have a family history of cardiovascular disease, high cholesterol levels, or other risk factors for heart disease. 

Patients who have not responded well to traditional cholesterol-lowering medications or have persistently high LDL cholesterol levels despite lifestyle modifications may also benefit from ApoB testing. Additionally, individuals with metabolic syndrome, diabetes, or obesity may be good candidates for ApoB testing, as these conditions are often associated with dyslipidemia and increased cardiovascular risk.

It is important to note that ApoB testing is not typically recommended as a routine screening test for the general population. However, in high-risk individuals, ApoB testing can provide valuable information about their cardiovascular health and guide treatment decisions. As always, it is best to consult with a healthcare provider or a functional medicine practitioner to determine if ApoB testing is appropriate for a specific patient.

What is a normal Apolipoprotein B range?

The normal range for ApoB can vary slightly depending on the laboratory and the method used for testing. However, in general, the normal range for ApoB is considered to be between 60 and 120 mg/dL (milligrams per deciliter). It is important to note that these values may vary slightly between different laboratories and testing methods. Leading lipidologists and cardiovascular health experts point out that the Framingham Offspring Study demonstrates that an optimal ApoB level is below 80 mg/dL.⁶ 

It is worth mentioning that ApoB levels are typically interpreted in conjunction with other lipid markers such as LDL cholesterol (LDL-C), triglycerides, total cholesterol, and possibly other specialized markers such as sdLDL. These markers provide a more comprehensive assessment of cardiovascular risk. 

It is important to consult with a healthcare professional or a functional medicine practitioner to interpret ApoB test results in the context of an individual's overall health and other risk factors. They can provide personalized recommendations and interventions to optimize cardiovascular health based on the ApoB levels and other relevant factors.

What does high Apolipoprotein B indicate?

Because Apolipoprotein B (ApoB) is a component of the atherogenic lipid particles VLDL, IDL, LDL, and lipoprotein a ,it’s an effective marker to assess a person’s risk of developing coronary heart disease.⁷⁸

A high  level of ApoB in the bloodindicates an increased concentration of atherogenic particles. This is concerning because these particles are known to contribute to the development of atherosclerosis, a condition characterized by the buildup of plaque in the arteries, including the coronary arteries (the blood vessels around the heart). Atherosclerosis can lead to various cardiovascular diseases and events, including heart attacks and strokes.

Elevated ApoB is often associated with other risk factors for cardiovascular disease including high total cholesterol, LDL cholesterol, triglycerides and insulin resistance. It is considered a more accurate marker of cardiovascular risk than measuring LDL cholesterol alone.

To manage high ApoB levels, lifestyle modifications are typically recommended. This includes adopting a healthy diet low in saturated and trans fats, increasing physical activity, maintaining a healthy weight, and quitting smoking. In some cases, medication may be prescribed to help lower LDL cholesterol levels and reduce the risk of cardiovascular events.

Regular monitoring of ApoB levels through lab testing can help assess the effectiveness of interventions and guide treatment decisions. It is important to work with a healthcare professional to interpret the results and develop an appropriate plan for managing high ApoB levels.

What does low Apolipoprotein B indicate?

A low level of apoB in the blood indicates a decrease in the number of atherogenic particles This can have positive implications for cardiovascular health as atherogenic particles are associated with an increased risk of developing atherosclerosis and heart disease.

A low apoB level may be a result of various factors, including:

Lifestyle modifications: Adopting a healthy lifestyle, including regular exercise, a balanced diet, and weight management, can lead to a reduction in apoB levels.

Medications: Certain medications, such as statins, can lower apoB levels by reducing the production of LDL particles in the liver.

Genetic factors: Some individuals may have genetic variations that naturally result in lower apoB levels.

Dietary changes: Consuming a diet low in saturated and trans fats, and high in fiber and healthy fats (such as omega-3 fatty acids), can help lower apoB levels.

Low ApoB levels are protective against coronary artery disease.  In rare cases, levels below 40 mg/dL may indicate familial hypobetalipoproteinemia (a genetic deficiency of apolipoproteins, including ApoB) which may cause neurological or hepatic manifestations.⁹

It is important to note that while a low apoB level is generally considered beneficial for cardiovascular health, it should be interpreted in the context of other lipid markers and overall health status. Consulting with a healthcare professional, such as a functional medicine practitioner, can provide a comprehensive understanding of the individual's lipid profile and guide appropriate interventions if necessary.

How ApoB Is Tested?

Access Medical Labs is CLIA (Clinical Laboratory Improvement Amendments) Certified and CAP (College of American Pathologists) Accredited, ensuring high standards of quality and accuracy in testing. Specifically, ApoB levels are determined using a Turbidimetric Immunoassay. This method involves the formation of a precipitate when an antigen-antibody reaction occurs, and the amount of light absorbed or transmitted through this precipitate is measured. This measurement reflects the concentration of ApoB in the blood sample.

Apolipoprotein B (ApoB) levels are an important indicator in evaluating cardiovascular risk and are measured through a blood test. Unlike some other tests, fasting is not typically required for an ApoB test, making it more convenient for patients. In many cases, to facilitate this process, a mobile phlebotomist service is available. They can visit the patient's location to collect the blood sample, ensuring minimal disruption to the patient's routine. After collection, the sample is expediently sent to a laboratory for analysis.

Results from this test are typically available within about 6 days, offering a relatively quick turnaround for patients and healthcare providers. Understanding ApoB levels is crucial as it provides insights into lipid particles responsible for plaque buildup in arteries, thereby helping in assessing the risk of cardiovascular diseases. This streamlined and precise testing method facilitates effective monitoring and management of cardiovascular health risks.

Sources

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3. Behbodikhah J, Ahmed S, Elyasi A, Kasselman LJ, De Leon J, Glass AD, Reiss AB. Apolipoprotein B and Cardiovascular Disease: Biomarker and Potential Therapeutic Target. Metabolites. 2021 Oct 8;11(10):690. doi: 10.3390/metabo11100690. PMID: 34677405; PMCID: PMC8540246.

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5. Ito Y. [Apolipoprotein B and small, dense LDL-C]. Rinsho Byori. 2012 Apr;60(4):336-42. Japanese. PMID: 22686043.

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7. Richardson TG, Sanderson E, Palmer TM, Ala-Korpela M, Ference BA, Davey Smith G, et al. (2020) Evaluating the relationship between circulating lipoprotein lipids and apolipoproteins with risk of coronary heart disease: A multivariable Mendelian randomisation analysis. PLoS Med 17(3): e1003062. https://doi.org/10.1371/journal.pmed.1003062

8. Pencina MJ, D'Agostino RB, Zdrojewski T, Williams K, Thanassoulis G, Furberg CD, Peterson ED, Vasan RS, Sniderman AD. Apolipoprotein B improves risk assessment of future coronary heart disease in the Framingham Heart Study beyond LDL-C and non-HDL-C. Eur J Prev Cardiol. 2015 Oct;22(10):1321-7. doi: 10.1177/2047487315569411. Epub 2015 Jan 29. PMID: 25633587.

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Additional references

Doonan LM, Fisher EA, Brodsky JL. Can modulators of apolipoproteinB biogenesis serve as an alternate target for cholesterol-lowering drugs? Biochim Biophys Acta Mol Cell Biol Lipids. 2018 Jul;1863(7):762-771. doi: 10.1016/j.bbalip.2018.03.010. Epub 2018 Apr 6. PMID: 29627384; PMCID: PMC5953829.

Michael E. Makover, Michael D. Shapiro, Peter P. Toth,

There is urgent need to treat atherosclerotic cardiovascular disease risk earlier, more intensively, and with greater precision: A review of current practice and recommendations for improved effectiveness,

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OLOFSSON, S.-.-O. and BORÈN, J. (2005), Apolipoprotein B: a clinically important apolipoprotein which assembles atherogenic lipoproteins and promotes the development of atherosclerosis. Journal of Internal Medicine, 258: 395-410. https://doi.org/10.1111/j.1365-2796.2005.01556.x

Schaefer EJ, Tsunoda F, Diffenderfer M, et al. The Measurement of Lipids, Lipoproteins, Apolipoproteins, Fatty Acids, and Sterols, and Next Generation Sequencing for the Diagnosis and Treatment of Lipid Disorders. [Updated 2016 Mar 29]. In: Feingold KR, Anawalt B, Blackman MR, et al., editors. Endotext [Internet]. South Dartmouth (MA): MDText.com, Inc.; 2000-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK355892/