Skip to Main Content

INTRODUCTION

  • Risk factors for thromboembolism may be genetic or acquired (Table 89–1).

  • Hereditary thrombophilia is a genetically determined increased risk of thrombosis. These same risk factors may predispose for complications of pregnancy (recurrent miscarriage, fetal death, etc.)

  • Up to 50% of patients presenting with a first deep venous thrombosis will have an abnormal laboratory test suggesting a thrombophilic defect, and patients with recurrent thromboses or with a strong family history are even more likely to have laboratory evidence of a thrombophilic state (Table 89–1).

  • Up to 16% of patients with thrombophilia have inherited more than one abnormality.

  • These inherited defects also interact frequently with acquired risk factors, such as inactivity, trauma, malignancy, or oral contraceptive use, to lead to clinical thrombosis.

  • There are several reasons tests for thrombophilia can be false positive, as listed in Table 89–2.

  • The relative risks for venous thromboembolism, arterial thrombotic events, and pregnancy complications are summarized in Table 89–3.

| Download (.pdf) | Print
TABLE 89–1 PREVALENCE OF COMMON HEREDITARY THROMBOPHILIA
  General Population Patients with VTE
Antithrombin, protein S, or protein C deficiency 1% 7%
Factor V Leiden

Whites: 4%–7%

Nonwhites: 0%–1%

21%
Prothrombin G20210A

Whites: 2%–3%

Nonwhites: 0%–1%

6%
Elevated FVIII:c levels 11% 25%
Mild hyperhomocysteinemia 5% 10%

FVIII, factor VIII; VTE, venous thromboembolism.

TABLE 89–2ACQUIRED CONDITIONS THAT CAN YIELD FALSE-POSITIVE THROMBOPHILIA TEST RESULTS
TABLE 89–3RELATIVE RISK ESTIMATES FOR COMMON HEREDITARY THROMBOPHILIAS AND VENOUS OR ARTERIAL THROMBOSIS AND PREGNANCY COMPLICATIONS

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.