title: The incidence of venous thromboembolism among Factor V Leiden carriers: a community-based cohort study.
abstract: While Factor V (FV) Leiden is a risk factor for venous thromboembolism (VTE), the incidence of VTE among FV Leiden carriers is uncertain. The objective of the study was to estimate the overall age-specific and pregnancy-related VTE incidence and the relative risk among FV Leiden carriers. In a community-based sample of 3424 south-eastern Minnesota residents, 230 (6.7%) were genotyped as FV Leiden carriers; 220 carriers (mean age = 68 years) could be matched to a non-carrier on age, gender, ethnicity and length of medical history. We performed a retrospective cohort study of carriers and non-carriers by reviewing the complete medical records in the community for demographic and baseline characteristics, pregnancies and live births, and first lifetime VTE. Over 14 722 person-years, 24 (10.9%) carriers developed VTE [overall incidence = 163 (95% CI 104, 242) per 100,000 person-years]. VTE incidence rates for ages 15-29, 30-44, 45-59 and > or = 60 years were 0, 61, 244 and 764 per 100,000 person-years, respectively (cumulative VTE incidence at age 65 years = 6.3%). VTE incidence for carriers did not differ significantly from that for non-carriers except for those > or = 60 years old (relative risk = 3.6; 95% CI 2.0, 6.0). There were 311 live births among 130 women carriers; no VTE events occurred during pregnancy or postpartum [incidence = 0 (95% CI 0, 1186) per 100,000 women-years]. Most FV Leiden carriers do not develop VTE. Among all carriers, those > or = 60 years old are at the highest risk for VTE. The incidence of VTE among asymptomatic women carriers during pregnancy is low and insufficient to warrant prophylaxis.
authors.affiliation: Division of Cardiovascular Diseases and Section of Haematology Research, Department of Internal Medicine, Mayo Clinic, 200 First Street, SW, Rochester, MN 55905, USA. heit.john@mayo.edu
authors.forename: J A
authors.initials: JA
authors.lastname: Heit
authors.forename: J L
authors.initials: JL
authors.lastname: Sobell
authors.forename: H
authors.initials: H
authors.lastname: Li
authors.forename: S S
authors.initials: SS
authors.lastname: Sommer
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D005165:Factor V / Q000235:genetics*; D005260:Female; D006579:Heterozygote; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D008910:Minnesota; D011336:Probability; D012189:Retrospective Studies; D016008:Statistical Distributions; D013923:Thromboembolism / Q000453:epidemiology / Q000235:genetics*; D020246:Venous Thrombosis / Q000453:epidemiology / Q000235:genetics*
chemical_list: C095381:factor V Leiden; D005165:Factor V