Medical Genetics

MTHFR (C677T) Variant

Genetic predisposing factors for venous thrombosis include elevated plasma homocysteine levels. Increased plasma homocysteine levels are associated with the C677T variant in the methylenetetrahydrofolate reductase (MTHFR) gene. Homozygosity for the C677T variant is associated with mild hyperhomocysteinemia. The increase in risk for venous thrombosis in homozygous individuals has not been defined.

Molecular analysis for the MTHFR (C677T) variant may be ordered individually or as part of a Thrombophilia Panel which includes the Factor V Leiden (R506Q) Mutation and the Prothrombin G20210A Mutation (Factor II).

Indications for Testing

Individuals with a personal history of hyperhomocysteinemia

Individuals with family members known to have the MTHFR (C677T) variant

Testing Methodology

Direct mutation analysis: Our laboratory utilizes polymerase chain reaction and fluorogenic target-specific hybridization. Melting curve analysis is performed to discriminate between the normal and mutant genotype.

Sensitivity

Approximately 30 – 40% of the population is heterozygous for the MTHFR (C677T) variant. Approximately 10 – 15% of individuals are homozygous for this variant.

Specimen Requirements

Blood: 5 cc collected in a purple top (EDTA) or yellow top (acid citrate dextrose) vacutainer tube. Do not centrifuge or freeze. Specimen may be refrigerated or stored at room temperature.