Coagulation Mutation Panel - Factor V, Factor II, MTHFR

Background

Hereditary changes in coagulation proteins can affect normal coagulation and lead to increased risk of venous thrombosis. Three coagulation proteins that have been identified to play a role in hypercoagulability are prothrombin (Factor II), Factor V Leiden, and methylenetetrahydrofolate reductase (MTHFR).

Prothrombin

Prothrombin (Factor II) is the precursor of the serine protease thrombin, a key enzyme in the processes of hemostasis and thrombosis that exhibits anticoagulant activities. The prothrombin gene is organized in 14 exons with a 5' upstream untranslated region (UTR) and the 3' UTR, which may play regulatory roles in gene expression. One genetic variation in the 3' UTR of the prothrombin gene, a G to A transition at nucleotide position 20210 (the last nucleotide of the mRNA) was found in 18% of selected patients with a personal and family history of venous thrombosis. Carriers of this mutation have higher plasma prothrombin levels than controls with the normal genotype. Elevated prothrombin levels may lead to an imbalance between the procoagulant, anticoagulant, and fibrinolytic system. This could result in increased rates of thrombin generation, and therefore lead to excessive growth of fibrin clots. The nt 20210 G>A sequence variation in the prothrombin gene is a moderate risk factor for venous thrombosis, and those with the variant have a 2.8-fold increased risk of venous thrombosis.

OMIM: 176930

Factor V Leiden

Activated protein C (APC) is a serine protease that limits clot formation during normal hemostasis by proteolytic cleavage of factors Va and VIIIa. In APC resistance, the patient's plasma does not exhibit the normal anticoagulant response to addition of APC. This phenotype has been shown to be associated with heterozygosity or homozygosity for a point mutation in the APC cleavage site of factor V (factor V Leiden) c.1691G>A, which predicts a protein change of R506Q and a factor V molecule that is not properly inactivated by APC. Individuals heterozygous for the Factor V Leiden mutation appear to be at a greater risk for thrombosis that becomes significant with increasing age. Individuals homozygous for the Factor V Leiden mutation have a high risk of thrombosis that occurs in adulthood and these patients may benefit from short-term prophylaxis with anticoagulants in risk situations such as pregnancy.

OMIM: 612309

Methylenetetrahydrofolate Reductase

An elevated homocysteine level is a risk factor for thrombosis and vascular disease. Homocysteine is normally metabolized by remethylation to methionine or by transsulfuration to cysteine. Elevated levels of homocysteine may occur because of inherited disorders which alter the enzyme activity of metabolism or because of nutritional deficiencies of vitamin B12, folate, or vitamin B6 necessary as cofactors. One inherited disorder affecting metabolism involves polymorphism in the enzyme methylenetetrahydrofolate reductase (MTHFR) resulting in a thermolabile variant identified as a C677T transition. Other variants have also been identified. The thermolabile variant MTHFR is the most common inherited disorder of folic acid metabolism. Its significance alone in the absence of an elevated homocysteine level is not well-established. Recurrent pregnancy loss has been identified in some women heterozygous or homozygous for the C677T MTHFR variant.

OMIM: 607093

Clinical Utility

Detection of hereditary mutations that affect normal coagulation. The test is done on peripheral blood specimens for confirmation of clinical diagnosis, carrier status or presymptomatic testing.

Methodology

Detection of various point mutations in coagulation proteins Prothrombin, Factor V and MTHFR is done as a panel. The SNPs and genotype are specifically determined by use of Hologic Invader technology.

Loci Tested

  • F2 3'UTR; g.20210 G>A
  • F5 g.1691G>A; R506G
  • MTHFR g.677C>T; A222V; (rs1801133)

Specimen Requirements

Peripheral blood collected in EDTA (purple top) is preferred, 3-10mL

Turnaround Time

Within 4-10 business days of receipt

CPT

Factor V 81241; Factor II 81240; MTHFR 81291

Shipment Must Include

Specimen
Requisition form
Patient pathology report

References

  1. Poort, et al. (1996), Blood 88: 3698 - 3703.
  2. Bertina, R., Koeleman, et al. (1994), Mutation in Blood Coagulation Factor V Associated With Resistance to Activated Protein C. Nature, vol. 369, p. 64 - 67
  3. Rosendaal, F., Koster, T., Vandenbroucke, J., and Reitsma, P. High Risk of Thrombosis in Patients Homozygous for Factor V Leiden (Activated Protein C Resistance). Blood, vol. 85, p. 1504 - 1508 (1995)
  4. Frosst P, et al. (1995), A candidate genetic risk factor for vascular disease: a common mutation in methylenetetrahydrofolate reductase, Nat Genet;10: 111-3.
  5. Jacques PF, et al. (1996) Relation between folate status, a common mutation in methylenetetrahydrofolate reductase and plasma homocysteine concentrations. Circulation 93: 7-9.
  6. Deloughery TG, et al. (1996) Common mutation in methylenetetrahydrofolate reductase. Correlation with homocysteine metabolism and late onset vascular disease. Circulation ;94:3074-8.
  7. Guba, S.C., Fink, L.M., Fonseca, V. (1998) Hyperhomocysteinemia: an emerging and important risk factor for thromboembolic and cardiovascular disease, Am. J. Clin. Pathol105: 709-722.
  8. Gudnason V, et al. (1998) C677T (thermolabile alanine/valine) polymorphism in methylenetetrahydrofolate reductase (MTHFR): its frequency and impact on plasma homocysteine concentration in different European populations. Atherosclerosis 1998; 136:347-54.