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Evidence summaries

Risk of Pulmonary Embolism Associated with Factor V (Fva) Leiden

The increase in the risk of isolated pulmonary embolism associated with factor V (FVa) Leiden may be smaller than that of deep vein thrombosis. Level of evidence: "C"

According to 5 studies summarized in an editorial 1 of the Lancet, the odds ratio for developing isolated pulmonary embolism in carriers of FVa mutation is consistently smaller (2.5, 95% CI 1.8 to 3.5) than the odds ratio for developing isolated deep vein thrombosis (OR 6.0, 95% CI 4.6 to 7.8) or deep vein thrombosis and pulmonary embolism (OR 5.2, 95% CI 3.6 to 7.5). According to one study, thrombosis occurred strikingly less often in the iliofemoral veins among factor V Leiden carriers (2.8% vs 23.2%, p<0.01) 2. In addition, thrombi in these patients were significantly smaller than in non-carriers.

    References

    • Bounameaux H. Factor V Leiden paradox: risk of deep-vein thrombosis but not of pulmonary embolism. Lancet 2000 Jul 15;356(9225):182-3. [PubMed]
    • Björgell O, Nilsson PE, Nilsson JA, Svensson PJ. Location and extent of deep vein thrombosis in patients with and without FV:R 506Q mutation. Thromb Haemost 2000 May;83(5):648-51. [PubMed]

Primary/Secondary Keywords