Friday, March 8, 2024

Apolipoprotein E (APOE) genotype, total blood

Description, Result format and Reference values Modification

Test code: 2279
Mnemonic code: APOEG

Effective update from 18/03/2024


Description: Apolipoprotein E (APOE) genotype, total blood

Result format:
    R1: Result
      DNA extraction from the sample received. ApoE genotyping using Real-Time PCR Lighcycler Roche following the protocol described by Aslandis and Schimitz with some modifications (High-Speed Apolipoprotein E Genotyping and Apolipoprotein B3500 Mutation Detection using Real-Time Fluorescence PCR and Melting Curves. Clinical Chemistry, 1999). The technique can detect genotypes: E2 / E2; E3 / E3; E4 / E4; E2 / E3; E2 / E4 and E3 / E4.
      The most common Apo E gene have been described alleles are E2, E3 and E4, which produce three isoforms of the protein, called E2 (present in 8-11%), E3 (in the 77% of the population) and E4 (in 12-15%). These three different alleles are inherited as codominant resulting different genotypes: E2/E2, E3/E2, E3/E3, E3/E4, E4/E4, E4/E2.
      The presence of the E4 isoform is associated with an increase in total cholesterol levels, and betalipoproteins, and therefore an increased predisposition to heart disease and Alzheimer's disease. E2 on the other hand, has a protective effect against these diseases.
      Version of Test: 19


Result format:
R1: Sample
R2: Result

Reference values:

Interpretation and recommendations
The major alleles of the APOE gene described are E2, E3 and E4. Its difference lies in the combination of two SNPs: rs429358 and rs7412), and as a result three isoforms of the protein are translated, called E2 (present in 8-11% of the population), E3 (in 77%) and E4 (in 12-15%). These three different alleles are inherited in a co-dominant manner resulting in different genotypes: E2/E2; E3/E3; E4/E4; E2/E3; E2/E4 and E3/E4.
The presence of the E4 isoform is associated with an increase in the levels of total cholesterol (hypercholesterolemia) and beta lipoproteins and, therefore, an increase in the predisposition or risk of suffering from atherosclerosis and cardiovascular disease and also late-onset Alzheimer's disease. E3 is a marker of the general population and E2, on the contrary, has a protective effect against these diseases as it is associated with low plasma cholesterol levels and type III hyperlipoproteinemia.
This report should be evaluated by a specialist in the context of all available clinical and family information in conjunction with other laboratory findings. Genetic counselling is recommended.
Test method
DNA extraction followed by real-time PCR amplification (CE-IVD commercial method) for detection of APOE gene regions including variants rs429358 c.388T>C and rs7412 c.526C>T according to reference sequence NM_000041.2 related to late onset Alzheimer, hyperlipidemia and hypercholesterolemia.
Test limitations
Variants other than those studied are not analyzed.
Normal/polymorphic genomic variation in the patient may interfere with variant detection in the sample.
Liu CC, et al. (2013). Nat Rev Neurol. 9 (2): 106-18.
Aslanidis C et al. (1999) Clin Chem. 45(7): 1094-7.

Version of Test: 20

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