title: Apparent different thrombotic tendency in patients with factor V Leiden and protein C deficiency due to selection of patients.
abstract: Both activated protein C (APC) resistance and protein C deficiency are associated with an increased risk for venous thrombosis. To assess their tendencies to venous thrombosis, we compared the median age of first venous thromboembolism in patients with factor V Leiden or protein C deficiency, who were identified either within unselected consecutive cases with a first deep venous thrombosis derived from a population-based case-control study, or identified by selection of patients with a deep venous thrombosis, who were referred for thrombophilIa work-up. The median age of onset for 92 unselected APC resistant cases was 43 years and for 13 unselected protein C-deficient cases 47 years. The median age at the first thrombotic event for 28 APC-resistant members of thrombophilia families was 29 years and for 50 protein C-deficient members of thrombophilia families 31.5 years. The median age of onset for all unselected patients (n = 105) was 45 years of age (range, 16 to 69 years) and the median age of onset for all selected patients from the thrombophilia families (n = 78) was 30.5 years (range, 16 to 67 years). These results show that within the case-control study and the family studies, the median age of onset is very similar in patients with APC resistance and patients with protein C deficiency. This suggests that APC resistance is not less severe with respect to risk of thrombosis than (heterozygous) protein C deficiency. In conclusion, the median age at which the first thrombosis occurs mainly depends on the way the patients are identified and not on the type of thrombophilia.
authors.affiliation: Department of Clinical Epidemiology, University Hospital Leiden, The Netherlands.
authors.forename: R P
authors.initials: RP
authors.lastname: Lensen
authors.forename: F R
authors.initials: FR
authors.lastname: Rosendaal
authors.forename: T
authors.initials: T
authors.lastname: Koster
authors.forename: C F
authors.initials: CF
authors.lastname: Allaart
authors.forename: H
authors.initials: H
authors.lastname: de Ronde
authors.forename: J P
authors.initials: JP
authors.lastname: Vandenbroucke
authors.forename: P H
authors.initials: PH
authors.lastname: Reitsma
authors.forename: R M
authors.initials: RM
authors.lastname: Bertina
mesh_terms: D000328:Adult; D000367:Age Factors; D017668:Age of Onset; D016022:Case-Control Studies; D004198:Disease Susceptibility; D005165:Factor V / Q000235:genetics*; D005166:Factor V Deficiency / Q000150:complications / Q000453:epidemiology* / Q000235:genetics; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011486:Protein C / Q000235:genetics*; D020151:Protein C Deficiency; D012306:Risk; D015983:Selection Bias; D013927:Thrombosis / Q000453:epidemiology* / Q000209:etiology
chemical_list: D011486:Protein C; C095381:factor V Leiden; D005165:Factor V