Interpretive Handbook

Test 80318 :
Apolipoprotein A1 and B, Plasma

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Apolipoprotein B (ApoB) is the primary protein component of low-density lipoprotein (LDL). Apolipoprotein A1 (ApoA1) is the primary protein associated with high-density lipoprotein (HDL). Both ApoB and ApoA1 are more strongly associated with cardiovascular disease than the corresponding lipoprotein cholesterol fraction (See APLA1 / Apolipoprotein A1, Plasma and APLB / Apolipoprotein B, Plasma). However, the most powerful risk prediction value of these proteins appears to be in their ratio (ie, ApoB:ApoA1).

 

ApoB is present in all atherogenic lipoproteins including LDL, Lp(a), intermediate-density lipoprotein (IDL), and very low-density lipoprotein (VLDL) remnants. ApoA1 is the nucleating protein around which HDL forms during reverse cholesterol transport. Therefore, the ApoB:ApoA1 ratio represents the balance between atherogenic and antiatherogenic lipoproteins. Several large prospective studies have shown that the ApoB:ApoA1 ratio performs as well, and often better, than traditional lipids as an indicator of risk.(1-3)

Useful For Suggests clinical disorders or settings where the test may be helpful

Assessment of residual risk in patients at target non-HDL-C (or LDL-C)

 

Follow-up studies in individuals with non-HDL-C (or LDL-C) values inconsistent with risk factors or clinical presentation

 

Definitive studies of cardiac risk factors in individuals with significant family histories of coronary artery disease or other increased risk factors

Interpretation Provides information to assist in interpretation of the test results

Reduced ApoA1 confers increased risk of coronary artery disease. ApoA1 <25 mg/dL may be helpful to aid in the detection of a genetic disorder such as Tangier disease.

 

Elevated ApoB:ApoA1 ratio confers increased risk of coronary artery disease.

 

Expected values in normal (no cardiovascular or genetic disease) adults are 48 to 124 mg/dL for ApoB and 106 to 220 mg/dL ApoA1.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Fasting for <12 hours or intake of alcohol during the 24 hours prior to specimen collection may invalidate test results.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

APOLIPOPROTEIN AI

> or =18 years: 106-220 mg/dL

Reference values have not been established for patients who are <18 years of age.

 

APOLIPOPROTEIN B

> or =18 years: 48-124 mg/dL

Reference values have not been established for patients who are <18 years of age.

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Reiner Z, Catapano AL, De Backer G, et al: ESC/EAS Guidelines for the management of dyslipidaemias: The task force for the management of dyslipidaemias of the European Society of Cardiology (ESC) and the European Atherosclerosis Society (EAS). Eur Heart J 2011;32(14):1769-1818

2. McQueen MJ, Hawken S, Wang X et al: Lipids, lipoproteins, and apolipoproteins as risk markers of myocardial infarction in 52 countries (the INTERHEART study): a case-control study. Lancet 2008;372:224-233

3. Thompson A, Danesh J: Associations between apolipoprotein B, apolipoprotein AI, the apolipoprotein B/AI ratio and coronary heart disease: a literature-based meta-analysis of prospective studies. J Intern Med 2006;259:481-492


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