The Factor V HR2 haplotype is defined by a number of polymorphisms:
(1) exon 13: 2298, 2325, 2379, 2391, 4070 (Bernardi et al)
(2) exon 16: 5380 (Bernardi et al)
(3) exon 25: 6755 (Pecheniuk et al)
Indications to test for the Factor V HR2 haplotype:
(1) abnormal APC resistance with absence of Factor V Leiden
(2) hypercoagulable state negative for other risk factors
(3) thrombosis with low Factor V levels
(4) family history of factor V HR2 haplotype
The significance of the HR2 haplotype is affected by several factors:
(1) heterozygous vs homozygous
(2) co-expression with Factor V Leiden
(3) plasma Factor V levels
(4) presence of other risk factors for thrombosis
