Prevalence of Factor V Genetic Variants Associated With Indian APCR Contributing to Thrombotic Risk

Phenotypic resistance to activated protein C (APC) is a complex mechanism associated with increased thrombosis risk. Activated protein C resistance (APCR) is mainly influenced by FV_Leiden mutation, and various other single nucleotide polymorphisms (SNPs) in FV gene are known to be associated with APCR. The aim of present study was to investigate the incidence and assess possible mechanisms of APCR in Indian patients with deep vein thrombosis (DVT). Three hundred and ten Doppler-proven patients with DVT were screened for APCR, and 50 APCR positive patients and 50 controls were typed for FV_Leiden, Hong Kong, Cambridge, HR2 haplotype, Glu666Asp, Ala485Lys, and Liverpool using either polymerase chain reaction (PCR)-restriction fragment length polymorphism or allele specific PCR. FV_Leiden was commonest cause of APCR (50%) in Indian patients with DVT being statistically significant ( P = .001) compared to controls. FV Liverpool, FV Glu666Asp and FV Ala485Lys were studied for the first time in Indian population. FV Liverpool, FV Glu666Asp, Hong Kong, and Cambridge were found to be absent. High frequency of Ala485Lys in patients shows that it might be a risk factor contributing to APCR in Indian patients with DVT. HR2 haplotype was not associated with APCR; however, presence of homozygous HR2 haplotype in patients only indicates the role it might play in Indian APCR population. In conclusion, contribution of FV_Leiden causing APCR in Indian population is not as strong as previously reported in Western countries. The presence of other SNPs observed in the present study requires such studies on larger sample size to understand the molecular basis of defect.