Traveler's Thrombosis: A Systematic Review

Mohammed T. Ansari; Bernard M.Y. Cheung; Jia Qing Huang; Bo Eklof; Johan P.E. Karlberg


J Travel Med. 2005;12(3):142-154. 

In This Article


Our conclusions correspond to those of a recent WHO consultation on air travel.[4] Although a precise magnitude of an association cannot be reached from this review, it is likely that it is fluctuant and dependent upon genetic, geographic, and cultural factors in the general population. Scandinavians flying to Australia, for example, will likely have a relatively higher risk of VTE associated with air travel. Of all other modes of transportation, air travel is believed to expose passengers to more unusual and thrombogenic environmental factors.[4]

Conclusions drawn from this review have their limitations related to the weakness inherent in the current published literature on TAVTE. Many studies were of low external validity. Since our search was limited to English-language studies only, language bias is probable. Further, we did not objectively evaluate for publication bias, even when not apparently evident. Conclusions have been drawn on the overall perspective rather than a grading of studies and pooling of statistics.

At this stage no definitive preventive measures can be advocated besides recommending frequent isometric foot and leg muscle contractions and adequate hydration on flights. Prophylactic clinical interventions, such as graduated stockings and heparin, should be instituted after individual clinical assessment only in passengers at high risk for VTE.

It is evident that studies so far have been ill designed and underpowered. Few previous case-control studies ensured data collection free of recall and diagnostic bias from incident rather than prevalent cases. When patients were employed as referents, systematic bias could have been reduced by adopting a range of control diagnoses. In retrospective reviews from hospital records, selection out of the study population would have underestimated the risk as some with disease could have died or moved out of the database because of the short observation periods. We concur with future research priorities identified by the WHO and programmed in the WRIGHT project that seek to assess the risk of prolonged air travel and natural history and pathophysiology of TAVTE from well-designed and adequately powered case-control, cohort, and experimental studies seeking intermediate end points.[4,5] Future research should preferably be extended to other modes of transportations as well.

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