Haplotypes of VKORC1, NQO1 and GGCX, their effect on activity levels of vitamin K-dependent coagulation factors, and the risk of venous thrombosis

a genome wide linkage analysis was performed in the selected pedigree for several coagulation factor levels and global coagulation determinants using the 'Sequential Oligogenic Linkage Analysis Routines' (SOLAR) program. The Leiden Thrombophilia Study (LETS)LETS is a population based case-control study, originally meant to investigate new risk factors of venous thrombosis.Between January 1988 and December 1992, 474 patients younger than 70 years from anticoagulation clinics in Leiden, Amsterdam and Rotterdam with a first DVT of the leg or arm were included in LETS.An unrelated control for each case was selected matched on age and sex.Participants did not have overt malignancy.All participants filled out a standard questionnaire regarding risk factors of venous thrombosis.The follow-up part of the LETS was performed to investigate the risk factors for recurrent venous thrombosis.Cases were followed as described previously 28 after anticoagulation cessation until January 2000.Information during followup on the occurrence of risk situations, use of anticoagulation treatment, and recurrent events was collected by repeated mailed questionnaires.