Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary 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. ++ Table Graphic Jump Location|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 Graphic Jump LocationTABLE 89–2ACQUIRED CONDITIONS THAT CAN YIELD FALSE-POSITIVE THROMBOPHILIA TEST RESULTSView Table||Download (.pdf) TABLE 89–2 ACQUIRED CONDITIONS THAT CAN YIELD FALSE-POSITIVE THROMBOPHILIA TEST RESULTS Test Acquired Conditions That Can Cause Abnormal Test Results Increased activated protein C (APC) resistance Pregnancy, use of oral contraceptives, use of direct thrombin or direct factor Xa inhibitors, stroke, presence of lupus anticoagulant, increased factor VIII levels, autoantibodies against APC Factor V Leiden — Prothrombin G20210A — Decreased level of protein C Liver disease, use of vitamin K antagonist (VKA), vitamin K deficiency, childhood, disseminated intravascular coagulation, presence of autoantibodies against protein C Decreased level of free protein S Liver disease, use of VKA, use of direct factor Xa inhibitors, vitamin K deficiency, pregnancy, use of oral contraceptives, nephrotic syndrome, childhood, presence of autoantibodies against protein S, disseminated intravascular coagulation Decreased level of antithrombin Use of heparin, thrombosis, disseminated intravascular coagulation, liver disease, nephrotic syndrome Hyperhomocysteinemia Deficiencies of folate (vitamin B11), vitamin B12, or vitamin B6; old age; renal failure; excessive consumption of coffee; smoking Increased factor VIII levels Pregnancy, use of oral contraceptives, exercise, stress, older age, acute-phase response, liver disease, hyperthyroidism, cancer ++Table Graphic Jump LocationTABLE 89–3RELATIVE RISK ESTIMATES FOR COMMON HEREDITARY THROMBOPHILIAS AND VENOUS OR ARTERIAL THROMBOSIS AND PREGNANCY COMPLICATIONSView Table||Download (.pdf) TABLE 89–3 RELATIVE RISK ESTIMATES FOR COMMON HEREDITARY THROMBOPHILIAS AND VENOUS OR ARTERIAL THROMBOSIS AND PREGNANCY COMPLICATIONS Relative Risk First VTE Recurrent VTE Arterial Thrombosis Pregnancy Complications Antithrombin deficiency 5–10 1.9–2.6 No ... Your Access profile is currently affiliated with [InstitutionA] and is in the process of switching affiliations to [InstitutionB]. Please select how you would like to proceed. Keep the current affiliation with [InstitutionA] and continue with the Access profile sign in process Switch affiliation to [InstitutionB] and continue with the Access profile sign in process Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Error: Incorrect UserName or Password Username Error: Please enter User Name Password Error: Please enter Password Sign in Forgot Password? Forgot Username? Sign in via OpenAthens Sign in via Shibboleth You already have access! Please proceed to your institution's subscription. Create a free profile for additional features.