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Factor V Genotyping Analysis

Factor V Leiden Mutation, FV, Factor V Leiden Genotyping

Test Codes

EPIC: LAB6383, SOFT: GFVG

Department

Molecular Pathology

Instructions

This test is available to outpatients only. For questions, please call 800-551-0488.

Specimen Collection Criteria

Collect: One 10 mL whole blood in Lavender-top EDTA tube. (Minimum: 5.0 mL)

Physician Office/Draw Specimen Preparation

Do not freeze specimens. Maintain whole blood at room temperature (20-26°C or 68-78.8°F) prior to transport.

Preparation for Courier Transport

Transport: Whole blood at room temperature (20-26°C or 68-78.8°F). (Minimum: 5.0 mL whole blood)

Rejection Criteria

• Frozen specimens. 
• Unlabeled tubes. 
• Specimens collected in heparin (Green-top), clot tubes (Red-top), or SST tubes.
• This test will only be performed once in a lifetime for a patient.

In-Lab Processing

Do not freeze specimens. Maintain specimen refrigerated (2-8°C or 36-46°F) prior to testing.

Storage

Specimen Stability for Testing:

Whole Blood
Room Temperature (20-26°C or 68-78.8°F): 72 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Extracted DNA may be available for additional testing if clinically indicated. Contact the Molecular Pathology Laboratory for verification.

Laboratory

Royal Oak Clinical Molecular Pathology Laboratory

Performed

Once per week.
Results available in 7–10 business days.

Reference Range

Negative (no mutations).

Test Methodology

Integrated sample purification, nucleic acid amplification, and detection of the target sequences using real-time Polymerase Chain Reaction (PCR).

Interpretation

The genetic basis for activated protein C (APC) resistance has been defined as a point mutation in the factor V gene at codon 506, the site where APC cleaves and inactivates the factor Va procoagulant. One or both copies of the factor V gene from patients with APC resistance thus carry a single G to A missense mutation converting arginine 506 to glutamine. After activation, this mutated factor V cannot be cleaved by APC; its procoagulant activity therefore persists and the risk of thrombosis increases significantly. The increased thrombotic risk associated with the heterozygous factor V mutation appears to be approximately 5-10 times the thrombotic risk of the normal population. The risk for patients carrying a homozygous factor V mutation may be up to 100 fold greater. Up to half of all patients with a history of thromboembolism have a functional APC resistance, the vast majority of these defects being attributable to the factor V mutation described. This mutation is prevalent (2 - 7% in the general population); the described factor V mutation is by far the most common cause of familial thrombotic syndromes.

Clinical Utility

• The Molecular Pathology Laboratory test is a rapid test for factor V gene analysis. The test is a detection of a mutation in the gene for Factor V which, if present, renders Factor V APC resistant and predisposes the patient to thrombosis.
• Testing for Factor V Leiden is recommended for:
  • Patients with history of recurrent venous thromboembolisms (VTE), patients with VTE at younger age (less than 50 years), unprovoked VTE at any age, VTE at unusual sites (cerebral, mesenteric, portal, hepatic, vena cava).
  • Patients with positive family history of VTE.
  • Women with VTE during pregnancy/post-partum, oral contraceptive, or hormone replacement therapy.
  • Women with unexplained pregnancy loss.
  • Prior to oral contraceptive use or pregnancy in asymptomatic females, first degree relatives of family member with identified mutation.
  • Children with venous or arterial thrombosis and children who are siblings of patients with early symptomatic VTE.
  • Patients with unexplained arterial thrombosis without atherosclerosis or young patients who smoke.

CPT Codes

81241
LOINC: 21668-9

Contacts

Last Updated

2/2/2022