Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1182 page)

PROTHROMBIN G20210A MOLECULAR MUTATION ASSAY
*

   Definition

   The prothrombin mutation
c.20210G
>
A
(
20210G
>
A
) in the
F2
gene is associated with increased plasma prothrombin levels and an increased risk of venous thrombosis (OMIM# 32790). Heterozygosity for the prothrombin
c.20210G
>
A
mutation is associated with an approximately threefold increased risk of venous thrombosis. Homozygosity for this mutation is rare, but the associated risk of venous thrombosis is likely to be higher than the heterozygous risk. Other factors can further increase the risk of thrombosis.

   
Normal values:
negative or no mutations are found.

   Use

   Prothrombin
c.20210G
>
A
testing should be performed in the following cases:

   A first venous thrombotic embolism (VTE) before age 50 years

   A first unprovoked VTE at any age

   A history of recurrent VTE

   Venous thrombosis at unusual sites such as the cerebral, mesenteric, portal, or hepatic veins

   VTE during pregnancy or the puerperium

   VTE associated with the use of oral contraceptives or hormone replacement therapy

   A first VTE at any age in an individual with a first-degree family member with a VTE before age 50 years

   Women with unexplained fetal loss after 10 weeks of gestation