Prothrombin 20210A Variant and Age at Thrombosis

Effect of elevated levels of coagulation factors on the risk of venous thrombosis in long-distance travelers

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 in travelers in a large case-control study. We calculated odds ratios (ORs) for 334 travelers (200 cases and 134 controls) with coagulation factors II (prothrombin), VII, VIII, and IX; fibrinogen, and von Willebrand factor (VWF) above the 80th percentile; for increasing numbers of risk factors; and for specific combinations. The risk was increased in travelers with high FII (OR, 2.2: 95% CI, 1.3-3.7) and FVIII (OR, 6.2, (95% CI, 3.6-10.5) compared with travelers with normal levels. High FIX and fibrinogen levels increased the risk in air travelers (FIX: OR, 3.2; 95% CI, 0.9-11.0; fibrinogen: OR, 2.0; 95% CI, 0.7-5.5) but not in other travelers. The ORs increased with the number of risk factors, and the risk was increased most in women with the combination of oral contraceptives and high FVIII (OR, 51.7; 95% CI, 5.4-498). We conclude that increased levels of FII and FVIII increase the risk of venous thrombosis in travelers. Furthermore, the risk is greatly increased if other risk factors are present as well.

Travel and venous thrombosis: a systematic review

In the past decade, numerous publications on the association between venous thrombosis (VT) and travel have been published. Relative and absolute risks of VT after travel, and particularly after travel by air, have been studied in case-control and observational follow-up studies, whereas the effect of prophylaxis has been studied through intervention trials of asymptomatic clots. The mechanism responsible for the association between travel and VT was addressed in pathophysiologic studies. Here, we systematically reviewed the epidemiologic and pathophysiologic studies about the association between travel and VT. We conclude that long-distance travel increases the risk of VT approximately two to fourfold. The absolute risk of a symptomatic event within 4 weeks of flights longer than 4 h is 1/4600 flights. The risk of severe pulmonary embolism (PE) occurring immediately after air travel increases with duration of travel, up to 4.8 per million in flights longer than 12 h. The mechanism responsible for the increased risk of VT after (air) travel has insufficiently been studied to draw solid conclusions, but one controlled-study showed evidence for an additional mechanism to immobilization that could lead to coagulation activation after air travel.

The scientific basis for evaluation and management of thrombotic disorders

The hemostatic mechanisms at work in the body involve a complex series of interactions between platelets, the endothelium, and the coagulation cascade. Much has been learned regarding the molecular mechanisms governing these intricate processes. The hypercoagulable state involves a disruption of the normal homeostatic equilibrium. This state may be either inherent or acquired. The prevention of associated thromboembolic complications requires therapeutic anticoagulation. A broader understanding of the factors contributing to these prothrombotic tendencies and the subtleties involved in their management provides the surgeon with another weapon in the armamentarium to promote better and safer patient outcomes.

The G20210A mutation of the prothrombin gene in patients with previous first episodes of deep-vein thrombosis: prevalence and association with factor V G1691A, methylenetetrahydrofolate reductase C677T and plasma prothrombin levels

A common G to A transition at nucleotide 20210 of the prothrombin gene is associated with an increased risk for deep-vein thrombosis (DVT) and high plasma levels of prothrombin. We calculated the prevalences of prothrombin G20210A, factor V G1691A (also associated with high risk for DVT) and homozygous methylenetetrahydrofolate reductase (MTHFR) C677T (associated with increased susceptibility to develop hyperhomocysteinemia) in 118 patients with a first episode of DVT and in 416 healthy controls. 15.9% of the patients and 2.3% of the controls had prothrombin G20210A (odds ratio [OR]: 8.7, 95% C.I.: 3.8-21.4); 21.1% of the patients and 3.2% of the controls had factor V G1691A (OR 7.8, 3.9-17.1); 20.5% of the patients and 21% of the controls had homozygous MTHFR C677T (OR: 1.0, 0.7-1.2). Exclusion of patients with other hereditary risk factors for DVT did not substantially modify the results. Mutant factor V and prothrombin coexisted in three patients but in no control. The concomitant presence of the MTHFR mutation did not increase the thrombotic risk associated with prothrombin G20210A. 63.2% of individuals with prothrombin G20210A had plasma levels of prothrombin in the upper quartile of distribution. After adjustment for age and sex, subjects with prothrombin levels in the upper quartile carried a slightly higher risk for thrombosis than those with lower prothrombin concentrations (OR: 1.9, 1.1-3.2). In conclusion, we found that prothrombin G20210A is relatively common in Italy and is associated with high prothrombin levels and an 8.7-fold increase in the risk for DVT. Such risk is independent of the coexistence of other known inherited risk factors for thrombosis and increases in patients with associated mutant factor V. Whether it is due to the associated increase in plasma prothrombin levels remains to be established.