Thrombophilia: How To Test? How To Manage?

By Julie Hambleton, MD

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Objectives

1. To understand the definition of thrombophilia and its limitations.
2. To identify individuals who may have an underlying thrombophilic state, either primary or secondary.
3. To identify the tests used to detect thrombophilia and their limitations.
4. To discuss the optimal duration of therapy for unprovoked venous thromboembolic disease.
5. To understand how the thrombophilia workup may impact the recommended duration of therapy.

Key words

anticoagulation therapy; deep venous thrombosis; genetic testing; hypercoagulable states; pulmonary embolus; thrombophilia

Abbreviations

APC = activated protein C; AT = antithrombin; DIC = disseminated intravascular coagulation; DVT = deep venous thrombosis; MTHFR = methylenetetrahydrofolate reductase; PC = protein C; PE = pulmonary embolus; PS = protein S; VTE = venous thromboembolic disease

The term thrombophilia implies an ongoing stimulus that predisposes an individual to thrombosis. This stimulus may be genetic (primary) in nature or acquired. Unfortunately, the genetic risk factors that characterize thombophilia are not uniform in their effects. Many individuals who carry thrombophilic conditions remain asymptomatic. Others who carry one or more of the genetic markers for a thrombophilic condition demonstrate a tendency for thrombosis, spontaneously or disproportionately to the thrombogenic stimulus. Finally, some individuals demonstrate an ongoing predisposition to recurrent thrombosis, yet have no identifiable thrombophilic defect. Individuals in these latter two categories may develop venous thromboembolic disease (VTE) at an early age, may suffer from recurrent deep venous thrombosis (DVT) and pulmonary embolus (PE), and may have family members who are similarly affected. Thrombophilia can be a particularly useful clinical concept in these instances.

The prothrombotic states may be acquired, inherited, or a combination of both. Acquired defects may be further categorized as intrinsic to the individual, such as cancer or presence of the lupus anticoagulant, or exogenous, such as estrogen therapy and surgery. These secondary risk factors may further interact with an individual's genetic predisposition, potentially enhancing the risk for thrombosis.

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