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Test Id : APOEG

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Apolipoprotein E Genotyping, Blood

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Overview

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

Determining the specific apolipoprotein E (APOE) genotypes in patients with type III hyperlipoproteinemia

 

APOE genotyping has been used to assess susceptibility for Alzheimer disease. However, the use of APOE analysis for predictive testing for Alzheimer disease is not currently recommended by the American College of Medical Genetics due to limited clinical utility and poor predictive value.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Name
A short description of the method used to perform the test

Polymerase Chain Reaction (PCR) including Restriction Digest

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.

Yes

Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Apolipoprotein E Genotyping, B

Aliases
Lists additional common names for a test, as an aid in searching

APOE

Dislipidemia

Dysbetalipoproteinemia

Dyslipidemia

Dyslipoproteinemia

Frederickson Type III

Hyperlipidemia Type III

Type III hyperlipoproteinemia

Alzheimer disease

Dementia

Specimen Type
Describes the specimen type validated for testing

Varies

Shipping Instructions

Specimen preferred to arrive within 96 hours of collection.

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Patient Preparation: A previous bone marrow transplant from an allogenic donor will interfere with testing. Call 800-533-1710 for instructions for testing patients who have received a bone marrow transplant.

Specimen Type: Whole blood

Container/Tube:

Preferred: Lavender top (EDTA) or yellow top (ACD)

Acceptable: Any anticoagulant

Specimen Volume: 3 mL

Collection Instructions:

1. Invert whole blood several times to mix blood. Do not aliquot.

2. Send specimen in original tube.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Forms

1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file.

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. Molecular Genetics: Neurology Patient Information

3. If not ordering electronically, complete, print, and send a Neurology Specialty Testing Client Test Request (T732) with the specimen.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

1 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Varies Ambient (preferred)
Frozen
Refrigerated

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

Determining the specific apolipoprotein E (APOE) genotypes in patients with type III hyperlipoproteinemia

 

APOE genotyping has been used to assess susceptibility for Alzheimer disease. However, the use of APOE analysis for predictive testing for Alzheimer disease is not currently recommended by the American College of Medical Genetics due to limited clinical utility and poor predictive value.

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

Apolipoproteins are structural constituents of lipoprotein particles that participate in lipoprotein synthesis, secretion, processing, and metabolism. Apolipoproteins have critical roles in blood lipid metabolism. Defects in apolipoprotein E (ApoE) are responsible for familial dysbetalipoproteinemia, or type III hyperlipoproteinemia, in which increased plasma cholesterol and triglycerides result from impaired clearance of chylomicron and very-low-density lipoprotein remnants.

 

The human APOE gene is located on chromosome 19. The 3 common APOE alleles are designated e2, e3, and e4, which encode the ApoE isoforms E2, E3, and E4, respectively. E3, the most common isoform in the White population, shows cysteine (Cys) at amino acid position 112 and arginine (Arg) at position 158. E2 and E4 differ from E3 by single amino acid substitutions at positions 158 and 112, respectively (E2: Arg158->Cys; E4: Cys112->Arg). The allele frequencies for most White populations are as follows:

-e2=8% to 12%

-e3=74% to 78%

-e4=14% to 15%

 

E2 and E4 are both associated with higher plasma triglyceride concentrations. Over 90% of individuals with type III hyperlipoproteinemia are homozygous for the e2 allele. However, less than 10% of individuals homozygous for the e2 allele have overt type III hyperlipoproteinemia. This suggests that other genetic, hormonal, or environmental factors must contribute to the phenotypic expression of the disease. The e4 allele has been linked to pure elevations of low-density lipoproteins. Patients with a lipid profile consistent with type III hyperlipidemia are candidates for analysis of their APOE genotype.

 

The APOE gene is also a known susceptibility gene for Alzheimer disease. The e4 allele is associated with an increased risk for Alzheimer disease, particularly late-onset disease, in a dose-dependent manner. This risk is also influenced by other factors. It is estimated that individuals with the APOE e3/e4 genotype have a 4-fold relative risk for Alzheimer disease, while homozygotes for e4 allele have a 12-fold relative risk. Several studies have suggested a protective effect of the APOE e2 allele.

 

The APOE e4 allele, however, is neither sufficient nor necessary for the development of Alzheimer disease.

 

Approximately 50% of individuals with Alzheimer disease carry an e4 allele, and many individuals who have an e4 allele will never develop Alzheimer disease. The use of APOE analysis for predictive testing for Alzheimer disease is not currently recommended by the American College of Medical Genetics and Genomics due to limited clinical utility and poor predictive value.

Interpretation
Provides information to assist in interpretation of the test results

An interpretive report will be provided.

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

This assay will not detect all of the genetic variants that cause type III hyperlipoproteinemia. Therefore, the absence of a detectable genetic variant does not rule out the possibility that an individual is a carrier of or affected with this disease.

 

This assay cannot predict or rule out the development of Alzheimer disease in an individual.

 

Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in the interpretation of results may occur if information given is inaccurate or incomplete.

 

Rare variants (ie, polymorphisms) exist that could lead to false-negative or false-positive results. If results obtained do not match the clinical findings, additional testing should be considered.

 

In rare cases, DNA alterations of undetermined significance may be identified.

  

This assay does not identify all of the less common apolipoprotein E alleles. Thus, an individual who appears to be homozygous for e2, e3, or e4 may carry one of the rare alleles that cannot be detected by this assay.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Smelt AH, de Beer F: Apolipoprotein E and familial dysbetalipoproteinemia: Clinical, biochemical, and genetic aspects. Semin Vasc Med. 2004 Aug;4(3):249-257

2. Utermann G: Morgagni lecture: genetic polymorphism of apolipoprotein E-impact on plasma lipoprotein metabolism In: Crepaldi G, Tiengo A, Baggio G. Diabetes, Obesity and Hyperlipidemias 3: Proceedings of the 4th European Symposium on Metabolism 1985. Elsevier; 1985:1-28

3. Elosua R, Ordovas JM, Cupples LA, et al: Association of APOE genotype with carotid atherosclerosis in men and women: the Framingham Heart Study. J Lipid Res. 2004 Oct;45(10):1868-1875

4. Poirier J, Davignon J, Bouthillier D, et al: Apolipoprotein E polymorphism and Alzheimer's disease. Lancet. 1993 Sep;342(8873): 697-699

5. Farrer L, Cupples A, Haines J, et al: Effects of age, sex, and ethnicity on the association between apolipoprotein E genotype and Alzheimer disease: a meta-analysis. JAMA. 1997 Oct 22-29;278(16):1349-1356

6. Goldman JS, Hahn SE, Catania JW, et al: Genetic counseling and testing for Alzheimer disease: joint practice guidelines of the American College of Medical Genetics and the National Society of Genetic Counselors. Genet Med. 2011 Jun;13(6):597-605

7. American College of Medical Genetics and Genomics: Five things physicians and patients should question. Choosing Wisely; 2015. Updated July 1, 2021. Accessed October 27, 2021. Available at www.choosingwisely.org/societies/american-college-of-medical-genetics-and-genomics/

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Description
Describes how the test is performed and provides a method-specific reference

A polymerase chain reaction-based assay, which includes HhaI digestion of the amplified product, is utilized to identify the 3 most common apolipoprotein E alleles (e2, e3, e4).(Unpublished Mayo method)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information

No

Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Wednesday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

9 to 10 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test

Rochester

Fees
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.

81401-APOE (apolipoprotein E) (eg, hyperlipoproteinemia type III, cardiovascular disease, Alzheimer disease), common variants (eg, *2, *3, *4)

LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
APOEG Apolipoprotein E Genotyping, B 42315-2
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
53198 Result Summary 50397-9
53199 Result 42315-2
53200 Interpretation 69047-9
53201 Reason for Referral 42349-1
53202 Specimen 31208-2
53203 Source 31208-2
53204 Released By 18771-6

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports