Factor XII deficiency not related to risk for VTE

Factor XII deficiency was not associated with risk for venous thromboembolism, according to data from a prospective study. However, elevated Factor XI was a risk factor for VTE.

“More work on the epidemiology and genetics of Factor XI in relation to VTE is needed, including clarification of any role of clinical testing of Factor XI level in people at risk for VTE,” the researchers wrote. “Testing of other factors studied here in clinical practice does not seem indicated.”

The researchers used two general population samples — participants from the Cardiovascular Health Study and the Atherosclerosis Risks in Communities study — to study the associations between coagulation Factors IX through XIII with the risk for future VTE. The samples were combined, yielding a total population of 21,860 participants; 462 subsequently developed VTE and 1,047 remained VTE-free. The researchers used pre-event blood samples to determine antigenic levels of coagulation Factors IX through XIII in these participants.

After adjusting for age, sex, race and study, the researchers determined that elevated Factor IX and XI levels were the only coagulation factors associated with an increased risk for VTE. The OR for Factor IX was 1.4 (95% CI, 1.0-2.0); for Factor XI the OR was higher at 2.0 (95% CI, 1.4-2.9). After further adjusting for BMI and diabetes, Factor XI was the only coagulation factor still associated with risk for VTE (OR=1.8; 95% CI, 1.3-2.7).

According to the researchers, associations were similar by study and whether thrombosis was idiopathic or secondary.

“The main finding of this prospective epidemiologic study is that among several procoagulant factors (IX through XIII) only elevated Factor XI was independently associated with increased risk of future VTE,” the researchers wrote. “This association was not confounded by levels of Factor VIIIc or D-dimer, which were strong VTE risk Factors in this study.”

Cushman M. Blood. 2009;doi:10.1182/blood-2009-05-219915