Venous thromboembolism in travellers: can we identify those at risk?
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To assess the prevalence of clinical and laboratory risk factors in patients who develop venous thromboembolism following travel. The design was a case series of 58 consecutive patients presenting with venous thromboembolism within 30 days of travel. The setting was a major metropolitan teaching hospital and an affiliated private practice. The main outcome measures were prevalence of clinical and laboratory risk factors for venous thromboembolism, time to presentation, mode and duration of travel. Forty-eight [83%; 95% confidence interval (CI), 71-91%] of 58 patients developed venous thromboembolism following air travel. Thirty-four (59%; 95% CI, 45-71%) patients had travelled for more than 8 h and most patients were diagnosed with venous thromboembolism within 1 week of completing their journey. Pulmonary embolism occurred in 24 patients (41%; 95% CI, 29-55%), proximal deep vein thrombosis in 23 patients (40%; 95% CI, 27-53%), calf vein thrombosis in four patients (7%; 95% CI, 2-17%), and superficial thrombophlebitis in seven patients (12%; 95% CI, 5-23%). At least one clinical or laboratory risk factor (other than travel) was found in 49 patients (84%; 95% CI, 73-93%) and two or more risk factors were found in 30 patients (52%; 95% CI, 38-65%). The most common risk factors were oestrogens (24%; 95% CI, 14-37%), a past history of thrombosis (24%: 95% CI, 14-37%), and factor V Leiden (24%: 95% CI, 14-37%). These retrospective uncontrolled data suggest that at least one clinical or laboratory risk factor is present prior to travel in more than 80% of patients who develop venous thromboembolism within 30 days of travel. In most cases these risk factors can be identified by the clinical history alone, without recourse to laboratory testing. Whether patients with known risk factors for venous thromboembolism prior to travel should be targeted with specific thromboprophylaxis requires randomized evaluation.