Apolipoprotein E (APOE) Genotyping, Alzheimer Disease Risk

Casandra

Casandra Test Code AR10664Version 1 (DRAFT)

Performing Lab

Lab ARUP LaboratoriesLab Test ID 2013341CPT Code 81401

Apolipoprotein E (APOE) Genotyping, Alzheimer Disease Risk

Also known as: APOE AZ

Clinical Use

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Use

This test is used to assess the risk of amyloid-related imaging abnormalities (ARIA) when prescribing amyloid-targeted antibody therapies, such as lecanemab and donanemab. It supports the clinical diagnosis of Alzheimer's disease (AD) in symptomatic individuals. APOE genotyping can be used for risk assessment, but results have limited clinical utility as APOE status alone cannot establish or exclude a diagnosis of AD. The e4 allele is associated with increased risk of AD, while the e2 allele may be associated with a lower risk for AD. However, the diagnosis of AD is primarily based on clinical evaluation, and APOE genotype alone is not sufficient to diagnose or exclude AD. The prevalence of APOE e4 heterozygosity and homozygosity is approximately 25% and 1-2% in the general population, respectively.

Special Instructions

Pre- and post-test genetic counseling is strongly recommended. Informed consent for genetic testing is required for New York patients. Counseling and informed consent forms are available online. Testing of fetal specimens or specimens from patients under the age of 18 years is not offered.

Limitations

Only the APOE alleles e2, e3, and e4 are detected; rare alleles are not detected by this test. Diagnostic errors can occur due to rare sequence variations. The test does not predict Alzheimer's disease risk in asymptomatic individuals and is not cleared or approved by the FDA. The presence of the e4 allele increases the likelihood of a correct diagnosis but is not diagnostic alone. Inheritance of APOE e4 is semi-dominant, with incomplete penetrance influenced by various factors including age, gender, and family history. The e4 allele is neither necessary nor sufficient for diagnosing AD. Most cases of dementia are multifactorial.

Test Details

New York Approved