Submitted June 2, 2008
Accepted November 4, 2008
The effect of elevated levels of coagulation factors on the risk of venous thrombosis in long distance travellers
Saskia Kuipers, Suzanne C Cannegieter*, Carine J.M. Doggen, and Frits R. Rosendaal
Department of Vascular Medicine, Academic Medical Center Amsterdam, Amsterdam, Netherlands
Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, Netherlands
Department of Thrombosis and Haemostasis, Leiden University Medical Center, Leiden, Netherlands
* Corresponding author; email: s.c.cannegieter{at}lumc.nl.
The risk of venous thrombosis is increased after long distance travel. Identifying high-risk groups may provide a basis for targeted prevention. We assessed the effect of increased levels of coagulation factors and combinations of risk factors on the risk of venous thrombosis in travellers in a large case-control study.
We calculated odds ratios for 334 travellers (200 cases and 134 controls) with coagulation factors II (prothrombin), VII, VIII and IX, fibrinogen and vWF above the 80th percentile, for increasing numbers of risk factors and for specific combinations of risk factors. The risk was increased in travellers with a high FII (OR 2.2, CI95 1.3-3.7) and FVIII (OR 6.2, CI95 3.6-10.5) as compared to travellers with normal levels. High FIX and fibrinogen levels increased the risk in air travellers (OR FIX 3.2, CI95 0.9-11.0; OR fibrinogen 2.0, CI95 0.7-5.5), but not in other travellers. The odds ratios increased with the number of risk factors and the risk was increased the most in women with the combination of oral contraceptives and high FVIII levels (OR 51.7, CI95 5.4-498).
From this case-control study in travellers, we conclude that increased levels of factors II and VIII increase the risk of venous thrombosis. Furthermore, the risk is greatly increased if other risk factors are present as well.
