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Factor V (Leiden) Mutation Analysis

Factor V (Leiden) Mutation Analysis

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Factor V (Leiden) Mutation Analysis

  

Clinical Use

  • Identify individuals at increased risk for venous and arterial thrombosis

  • Identify individuals at increased risk for pregnancy-associated complications

  • Identify individuals at risk from oral contraceptive use

  • Confirm positive activated protein C resistance (APCR) test results, especially in patients with lupus anticoagulant

Clinical Background

The factor V (Leiden) mutation (1691G>A) occurs primarily in white populations and is a major risk factor for venous thrombosis (21% frequency in affected individuals) and a lesser risk factor for arterial thrombosis (cardiovascular disease). The mutation is also highly associated with increased complications during pregnancy and puerperium. Such complications include severe preeclampsia, placental abruption, fetal growth retardation, recurrent miscarriage, stillbirth, and maternal pulmonary embolism and death. Due to a synergistic increase in venous thrombosis risk, individuals heterozygous for the factor V mutation are at greater risk when taking oral contraceptives.

The factor V mutation leads to replacement of Arg506 with Gln (R506Q) and APCR. Since laboratory tests for APCR are highly sensitive and specific and simpler to perform, APCR is usually the test of choice; however, factor V mutation analysis is recommended to confirm positive APCR tests. It is also recommended in place of APCR for pregnant patients and those with lupus anticoagulant, since such patients often have a false-positive APCR test result.

Method

The factor V gene region is amplified by PCR in the presence of a HyBeacon® probe specific for the mutated sequence. The melting temperature (Tm) of the probe-target complex is then determined using melting curve analysis. Presence of the factor V (Leiden) mutation results in a higher Tm than that obtained with the wild-type sequence.

Interpretive Information

The factor V (Leiden) mutation leads to the laboratory finding of APCR and is associated with a 4- to 8-fold increase in venous thromboembolic events in heterozygous individuals and a 50- to 100-fold increase in homozygous subjects. When a heterozygous mutation is coupled with oral contraceptive use, risk increases synergistically to 30-fold. Risk also increases synergistically when the mutation is coupled with increased homocysteine levels or with the factor II (prothrombin) 20210G>A mutation. Additionally, factor V is associated with arterial thrombosis (especially in smokers), complications of pregnancy (including fetal loss), and increased levels of factor VIII. Although this test is highly specific, identification of a mutation may occur in the absence of APCR in rare cases. Sensitivity of this test for APCR is 94%; thus, a negative result does not rule out APCR or an increased risk of venous thrombosis.

Mutation analysis is not affected by heparin, oral anticoagulants, pregnancy, oral contraceptives, estrogen replacement therapy, or lupus anticoagulants.
 

This test was developed and its performance characteristics have been determined by Quest Diagnostics Nichols Institute. It has not been cleared or approved by the U.S. Food and Drug Administration. The FDA has determined that such clearance or approval is not necessary. Performance characteristics refer to the analytical performance of the test.

Content reviewed 02/2013

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