CLINICAL TRIALS AND OBSERVATIONS Coagulation factors IX through XIII and the risk of future venous thrombosis: the Longitudinal Investigation of Thromboembolism Etiology

Higher levels of procoagulant factors and factor XII deficiency may be risk factors for first venous thromboembolism (VTE). We studied associations of coagulation factors IX through XIII with risk of future VTE in 2 general population samples. Using a nested case-control study com-bining the 21 860 participants of the Ath-erosclerosis Risk in Communities study and the Cardiovascular Health Study, we determined antigenic levels of these co-agulation factors in primarily pre-event blood samples from 462 participants who subsequently developed VTE and 1047 participants who remained free of VTE. Only elevated levels of factors IX and XI were associated with increased risk of VTE after adjustment for age, sex, race, and study. For factor IX, the odds ratio (OR) was 1.4 (95 % confidence inter-val [CI], 1.0-2.0) comparing the top to bottom quintile. The OR for factor XI was higher: 2.0 (95 % CI, 1.4-2.9). With further adjustment for body mass index and dia-betes, only elevated factor XI remained associated with VTE risk: OR 1.8 (95 % CI, 1.3-2.7). Associations were similar by study and whether the thrombosis was idiopathic or secondary. Factor XII defi-ciency was not related to VTE risk. Among these procoagulant factors, only elevated factor XI was a risk factor for VTE. (Blood. 2009;114:2878-2883