Apolipoprotein E Genotyping

Diagnostic Use

All requests for this testing will be assessed by a Pathologist before being approved for testing to proceed. Self referrals will not be accepted. Please see here for further details.

Elevated total cholesterol and triglyceride levels not responsive to dietry and lifestyle changes or a known family history of Type III hyperlipoproteinemia.

Apolipoprotein E (ApoE) is a polymorphic protein associated with plasma IDL and chylomicrons. Human apoE is genetically controlled by three alleles (E2, E3 and E4) at the single gene locus on chromosome 19. Six genotypes, resulting from the combination of any two alleles are possible. Individuals homozygous for the E2 allele are at increased risk of developing Type III hyperlipidaemia.

Department

Genetics - Molecular Pathology

Delphic Registration Code

ALEG

Synonyms

Apo E
hyperlipidaemia
Type III hyperlipidaemia

Turnaround Time

4 weeks

Test Code

4192

Specimen Type

• Whole Blood

Specimen Requirements

Tube/Container Type:

Preferred

• EDTA (Lavender Cap)

Preferred Sample Volume (ml)

4.0

No of Samples Required

1

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

• EDTA (Lavender Cap)

Preferred Sample Volume (ml)

1.0

Minimum Sample Volume (ml)

0.5

Additional Specimen Information

This genetic test requires nucleated cells. Please do not centrifuge or freeze the EDTA blood tube.
If storing blood tube prior to delivery please refrigerate at 4 degrees (transport still at ambient temperature).

Aliquot Instructions

Sample Type

• Whole Blood

Transport to Lab

Ambient (8 - 24 degrees Celsius)

Additional Referral/Aliquot Information

This genetic test requires nucleated cells. Please do not centrifuge or freeze the EDTA blood tube.
If storing blood tube prior to delivery please refrigerate at 4 degrees (transport still at ambient temperature).

Interpretation

Apo E genotyping is indicated in the diagnostic work-up of certain uncommon dyslipidaemia: the homozygous e2 genotype is associated with type III hyperlipidaemia.  The e4 allele is associated with Alzheimer disease (AD). However, Apo E genotyping is not part of the diagnostic work up for Alzheimer’s disease. The predictive value of apo E genotyping is too low for this test to be useful in the diagnosis of AD in symptomatic patients nor should it be performed in asymptomatic patients. Testing in asymptomatic individuals may cause harm and should not be performed. This position is supported by international consensus statements.^1-3

1. Genetic testing for Alzheimer’s disease, Panegyres PK et al. Med J Aust 2000; 172 (7): 339-43
2. Statement on Use of Apolipoprotein E Testing for Alzheimer Disease. Farrer, LA et al. JAMA. 1995;274(20):1627–1629
3. Apolipoprotein E genotyping in Alzheimer’s disease, National Institute on Aging/Alzheimer’s Association Working Group, Lancet 1996;347(9008):1091-1095

Test Method

Coding regions of exons flanking the region of interest in exon 4 of the APOE gene are amplified by PCR and analysed by automated fluorescent bi-directional DNA Sequencing.

The analysis determines the patient’s APOE genotype with respect to the three main APOE alleles: E2, E3 and E4 caused by substitution at the 130 and 176 amino acid positions only. Other mutations in the apoE gene may not be detected.

Contact Canterbury Health Laboratories on +64 3 364 0484 or email LabInfo@cdhb.health.nz

Additional Costing Information

Please contact this laboratory for current pricing.

Criteria for acceptance:
• Requests from specialist neurologists, psychiatrists, geriatricians, geneticists, cardiologists, and chemical pathologists will be approved.
• For requests from General Practitioners the clinical indication for testing must be clearly stated on the request form.
• The laboratory will not accept requests without a referral from a doctor.

Uncertainty of Measurement:
Automated bidirectional DNA sequencing has an analytical sensitivity and specificity of >99%. Note that the lower limit of variant detection of sequencing analysis is ~10%, this is important to consider in the case of mosaicism, mitochondrial, and somatic variation that is not expected to be present at 50% or 100%. This analysis will not detect variants located within intronic regions, except at the intron-exon boundaries.

Contact Information

Enquiry Form