How is a hypercoagulable state diagnosed?
Careful Medical History
Certain conditions increase a person’s risk for developing blood clots, but do not necessarily indicate a genetic hypercoagulable state. Therefore, a careful evaluation of the patient’s personal and family medical history is needed.
Patients may be candidates for screening for hypercoagulable states if they have:
- A family history of abnormal blood clotting
- Abnormal blood clotting at a young age (less than age 50)
- Thrombosis in unusual locations or sites, such as veins in the arms, liver (portal), intestines (mesenteric), kidney (renal) or brain (cerebral)
- Blood clots that occur without a clear cause (idiopathic)
- Blood clots that recur
- A history of frequent miscarriages
- Stroke at a young age
If you have one of the previously listed conditions, your doctor may recommend blood tests to further evaluate your condition.
These tests should be performed at a specialized coagulation laboratory and interpreted by a pathologist or clinician with expertise in coagulation, vascular medicine or hematology.
Ideally, the tests should be done when you are not having an acute clotting event.
The most common lab tests include:
- PT-INR: The prothrombin time (PT or protime) test is used to calculate your International Normalized Ratio (INR). The information is used to monitor your condition if you are taking warfarin (Coumadin). Your INR will help your healthcare provider determine how fast your blood is clotting and whether your warfarin (Coumadin) dose needs to be changed.
- Activated partial thromboplastin time (aPTT): Measures the time it takes blood to clot. This test is used to monitor your condition if you are taking heparin.
- Fibrinogen level
- Complete blood count (CBC)
Some of the tests help detect the antiphospholipid antibody syndrome or dysfibrinogenemias- conditions that can be associated with hypercoagulable states.
Tests used to help diagnose inherited hypercoagulable states include:
- Genetic tests, including factor V Leiden (Activated protein C resistance) and prothrombin gene mutation (G20210A)*
- Antithrombin activity
- Protein C activity
- Protein S activity**
- Fasting plasma homocysteine levels
*Factor V Leiden and prothrombin gene mutation (G20210A) are the most commonly identified genetic defects that increase a person’s risk for blood clotting.
**Additional lab tests, such as measurement of free (active) and total protein S antigen levels, may be required in order to validate protein S activity assay results.
Other tests used to help diagnose acquired hypercoagulable states include tests for:
- Anticardiolipin antibodies (ACA) or beta-2 glycoproteins, which are part of the antiphospholipid antibody syndrome*
- Lupus anticoagulants (LA), part of the antiphospholipid antibody syndrome*
- Heparin antibodies (in patients who develop low platelet counts while exposed to heparin)
*The presence of antiphospholipid antibodies (ACA) and a lupus anticoagulant (LA) is important when evaluating someone who has had recurrent miscarriages and venous or arterial thrombosis.
Testing helps identify whether the patient is at risk for further clotting and helps determine an appropriate course and length of treatment to prevent future clots. Testing also may help to identify relatives who don’t currently have symptoms but may be at risk.