Factor V Leiden (G1691A) Mutation, By PCR, Blood

Activated protein C resistance, which leads to thrombophilia, is due to a single mutation at nucleotide 1691 (CGA -> CAA) in the Factor V gene resulting in the replacement of the normal arginine at position 506 by a glutamine. This replacement makes Factor Va resistant to inactivation by Protein C. Factor V (not Va) is also a cofactor for protein C in the inactivation of factor VIIIa. This activity as a cofactor is lost as a result of the mutation. Thus, the mutation leads to factor Va and factor VIIIa resistance to inactivation by protein C. See Also Activated Protein C Resistance (Factor V Leiden), Plasma and Protein C Antigen Assay

This test is useful in the differential diagnosis of hereditary thrombophilia. Around 20% of heterozygotes and 40% of homozygotes develop thrombosis at an average age of 36 and 25 respectively. The relative risk of venous thrombosis for carriers of this mutation is estimated to be 5-10 fold increase for heterozygote and 50-100 fold increase for homozygote individuals.

2 ml EDTA Whole Blood Room Temperature

Collect in EDTA vacutainer tube. Avoid contamination with DNA of phlebotomist. Avoid haemolysed samples. Do not freeze samples. Send tube unopened.

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