Reference Range

NORMAL:  Normal Factor V function.  Although the Factor V Leiden mutation is absent, the individual may have other genetic and environmental risk factors for thrombosis.  If clinically indicated, further investigation may be necessary.
 

HETEROZYGOUS:  This individual does have the factor V Leiden mutation on one allele.
Heterozygous genotype for Factor V Leiden causes a resistance to activated protein C.  These individuals have a 5 – 10 fold increased risk of venous thrombosis.  If Prothrombin Gene Mutation (Factor II) is also present, then the risk of venous thrombosis is even higher.
FEMALES ONLY:  Women who are pregnant and heterozygous for Factor V Leiden have a 5 – 10 fold increase in venous thromboembolism.
 

HOMOZYGOUS:   This individual does have the Factor V Leiden mutation on two alleles.
Homozygous genotype for Factor V Leiden causes great resistance to activated protein C.  These individuals have a 50 – 100 fold increased risk for venous thrombosis.  If Prothrombin Gene Mutation (Factor II) is also present, the risk of thrombosis is even greater.
FEMALES ONLY:  Women with homozygous Factor V Leiden mutation have a substantially increased risk of clotting in pregnancy (and on estrogen-containing birth control pills or hormone replacement) in the form of deep vein thrombosis and pulmonary embolism.  They also may have an increased risk for preeclampsia, may have a small increased risk of low birth weight babies, may have a small increased risk of miscarriage and still birth due to either clotting in the placenta, umbilical cord, or the fetus.