Definition

The A4070G (His1299Arg) change located in exon 13 of the F5 gene is a polymorphism known as the 'R2 allele'. On its own it does not significantly increase the risk of venous thrombosis, but in heterozygous individuals who also carry the Factor V Leiden (R506Q) mutation, it creates additional activated protein C resistance and can multiply thrombosis risk; the allele frequency in the general population is approximately 10 percent.

Gene/region examined

FV - H1299R

Method

Sequence analysis

Accepted sample types

EDTA blood

Inheritance

Hereditary (germline), autosomal, a risk factor/polymorphism without full penetrance.

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Inheritance Patterns

Describes how a genetic condition is passed on within a family. There are five main patterns

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Carrier (Heterozygous / Homozygous)

Why it matters: In autosomal recessive inheritance, when each parent is a carrier (while both appear healthy), the chance of their child being born with the disease is 25% in each

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VUS (Variant of Uncertain Significance)

This is the situation where the test has detected a change in the DNA, but the role of this change in the development of disease is unconfirmed.

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How to Read a Genetic Test Result (Positive / Negative / VUS)

A genetic test result falls into three main categories

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Types of Genetic Tests

A genetic test is a type of medical test that detects changes in genes, chromosomes or proteins. Today there are more than 77,000 genetic tests available.

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