Diagnosis of Hemostasis and Thrombosis
A history and physical begins any diagnostic process, and thrombotic disease is no exception. Painful calf muscles may not require imaging to diagnose thrombophlebitis, but more information is better than less information, and when there is any doubt or when the severity of thrombotic disease needs to be assessed, there are two general approaches toward evaluation:
- Establishing the presence of thrombi in the venous or arterial system
- Evaluating the blood for hypercoagulable state
Thrombosis is confirmed with imaging studies:
- Ultrasound: Sound waves that can demonstrate the physical presence of a clot in a vein or artery but also evaluate the compromise of blood flow using Doppler technology. This is best used in thrombophlebitis (vein thrombosis)
- CT Angiography: CT is the process of assembling X-rays into layered images, useful for angiography, especially coronary or carotid angiography
- MRI: Also accurate in diagnosing the presence of thrombi, but less used due to expense or availability
A hypercoagulable state toward thrombosis can be one that affects coagulation and the likelihood of thrombus formation systemically, as with general clotting tendencies that are present from genetics (gene mutations, antithrombin deficiency), medication (estrogen), pregnancy, kidney disease, smoking, obesity, age, inflammatory bowel disease, vitamin metabolism (vitamin K), or elevated clotting factors.
Locally, a hypercoagulable state toward thrombosis can be limited to one area from immobility, surgery, varicose veins, malignancy, trauma, IV drug abuse, or infection.
Blood tests for hypercoagulability (“thrombophilia”) are usually individualized for each patient, but are useful in persons who have already suffered a thrombus or who have a family history of venous thromboembolism:
- Complete blood count, platelet count, and routine coagulation studies (PT and INR, aPTT)
- Inheritable thrombophilia panel: Gene mutations, protein deficiencies, and antithrombin deficiency
- Tests for hidden malignancy
- Antiphospholipid syndrome: Increasing the risk of venous and arterial thromboemboli
- Inflammatory markers such as erythrocyte sedimentation rate (ESR): Can suggest a malignancy or connective tissue disease
- Bleeding time: An older test which times how long blood takes to clot in a test tube. It is primarily used a screen for defects in coagulation
Anticoagulation Tests During Treatment
Once anticoagulation is begun for thrombotic disease, the manipulation of the clotting process is assessed via blood tests that determine how much slower the clotting process occurs:
- PT: Prothrombin time measures the time for plasma to clot when exposed to tissue factor.
- INR: The international normalized ratio is a PT ratio applied to a world-wide standard and measures how well the PT is affected by anticoagulants. It is expressed in the multiples of decreased speeds from normal clotting. The therapeutic goal for anticoagulation is an INR of 2-3 (ideally, 2.5). Because it is an international standard, it is especially useful for travelers.
- APTT: activated partial thromboplastin time measures the time for plasma to clot after exposure to contact factors.