Factor V Leiden detection in patients presenting with thrombotic episodes:Clinical characteristics

The factor V Leiden mutation is the most frequent cause of inherited thromb ophilia. Although the molecular lesion and its effects on the factor V prot ein are known, data on the associated clinical manifestations are limited. This study attempts to evaluate the prevalence of this mutation in patients presenting with thromboembolic disease and correlate the genotypic finding s with clinical characteristics. Peripheral blood specimens were collected from 746 patients between May 1995 and April 1998. The factor V genotypes w ere determined using polymerase chain reaction amplification, Mnl I digesti on, and electrophoretic separation of the allele-specific band patterns. Th e prevalence of the factor V Leiden mutation was found at 13.4% in this pat ient group, with 11.7% heterozygotes and 1.7% homozygotes and an approximat ely equal male and female incidence. Sites of thrombosis were predominantly venous; arterial events were rare. The recurrence rate for thrombosis seen in both homozygotes and heterozygotes was high, at 44% and 57%, respective ly. An important fraction of patients with the factor V Leiden mutation (45 %) had additional risk factors for thrombosis or precipitating/triggering e vents. Go-existence of additional genetic risk factors (antithrombin III, p rotein C and S deficiencies) was also found in 14.5% of patients with the L eiden mutation. In conclusion, identification of heterozygotes and homozygo tes for this mutation is important in the overall assessment of patients wi th thrombophilia and in patient management and counseling.