Genetic risk factors are involved
in the predisposition of individuals to venous thrombosis. Our laboratory
offers a thrombophilia panel which includes the following thrombosis risk
factor mutations: the Factor V Leiden R506Q mutation, Prothrombin (Factor
II) 20210 G-A mutation, and the MTHFR 677 C-T variant.
The most common mutation associated with inherited thrombosis in the Caucasian
population is the Factor V Leiden mutation, which leads to resistance to
activated protein C. Heterozygotes for the Factor V Leiden mutation have
an approximately 5 to 10-fold increased risk for venous thrombosis. The
second most common mutation associated with hereditary thrombosis is the
20210 G-A mutation in the prothrombin (Factor II) gene, which is associated
with increased plasma prothrombin levels. Heterozygote carriers of the prothrombin
20210 G-A mutation have an estimated 3 to 8-fold increased risk for venous
thrombosis. In addition, compound heterozygosity for both the Factor V Leiden
and the prothrombin 20210 G-A mutations tends toward earlier onset of thrombosis
and greater severity as compared to the presence of either mutation alone
in the heterozygous state. Another risk factor for venous thrombosis is
increased plasma homocysteine levels, which is associated with homozygosity
for a nucleotide variant in the methylenetetrahydrofolate reductase (MTHFR)
gene. The MTHFR 677 C-T variant (leading to an alanine to valine substitution)
results in a thermolabile enzyme and decreased production of folate, which
is a cofactor required for homocysteine remethylation. As an alternative
to the panel, analysis for these tests may be ordered on an individual basis
(See Factor V Leiden, Prothrombin, MTHFR
677 C-T variant).
Reasons For Referral:
- Evaluation of patients with
venous thrombosis
- Evaluation of venous thrombosis
in pregnant women or women taking oral contraceptives
- Evaluation of female
smokers with myocardial infarction under age 50
- Evaluation of asymptomatic
individuals with a family history of venous thrombosis
- Evaluation of
individuals with relatives known to have a thrombophilia risk factor
mutation
- Evaluation
of women with recurrent pregnancy loss, unexplained severe preeclampsia,
intrauterine fetal growth retardation, or stillbirth
Testing Methodology:
Direct Mutation Analysis: Our laboratory
uses DNA amplification (PCR) and an automated mini-sequencing methodology,
Pyrosequencing, to test for the Factor V Leiden R506Q mutation, prothrombin
(Factor II) 20210 G-A mutation, and the MTHFR 677 C-T variant.
Blood: EDTA (purple top) tubes: Adult: 14cc.
Requistion form must accompany specimen. Prior to any genetic testing,
we recommend genetic counseling and request that the subject sign our
consent form and submit it with the sample. To receive our forms, additional
information, or collection kits, please contact our laboratory. Turnaround Time: 3 weeks
Factor V, Prothrombin & MTHFR: 83904x3, 83912, 83898x3,
83891
Forms:
>> DNA
Requisition
Test Codes:
Factor V, Prothrombin & MTHFR: 6062
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