From the Guidelines
Procoagulant disorder testing should include a comprehensive panel of tests to identify hypercoagulable states, with initial evaluation consisting of a complete blood count, prothrombin time (PT), activated partial thromboplastin time (aPTT), and fibrinogen level, as recommended by the most recent study 1.
Initial Evaluation
The initial evaluation should include:
- Complete blood count
- Prothrombin time (PT)
- Activated partial thromboplastin time (aPTT)
- Fibrinogen level
Inherited Thrombophilias
For suspected inherited thrombophilias, specific tests include:
- Factor V Leiden mutation
- Prothrombin G20210A mutation
- Protein C activity
- Protein S activity
- Antithrombin III activity
- Homocysteine levels
Acquired Thrombophilias
For acquired thrombophilias, testing should include:
- Lupus anticoagulant
- Anticardiolipin antibodies
- Anti-beta-2 glycoprotein antibodies
Timing of Testing
Testing should ideally be performed at least 2-3 months after an acute thrombotic event and, if possible, after discontinuation of anticoagulant therapy to avoid false results, as suggested by 1 and 1.
Interpretation of Results
Testing should be interpreted in the clinical context, considering the patient's age, personal and family history of thrombosis, and presence of other risk factors, as recommended by 1 and 1. Certain medications like warfarin can affect Protein C and S levels, while heparin can affect antithrombin levels.
Additional Considerations
The most recent study 1 highlights the importance of considering the population age, gender, renal function, bioavailability, and pharmacodynamics-kinetics when interpreting coagulation assays. Viscoelastic coagulation tests, such as thromboelastography (TEG) and rotational thromboelastogram (ROTEM), can be useful in detecting coagulopathy associated with direct oral anticoagulants (DOACs) and guiding reversal therapy, as suggested by 1.
From the Research
Pro Coagulant Disorder Tests
- Prothrombin time (PT) and activated partial thromboplastin time (APTT) are the most widely used tests to investigate coagulation abnormalities 2
- PT results can be reported as clotting time, percentage activity, PT-ratio, or international normalized ratio (INR), while APTT is reported as clotting time or ratio 2
- The INR scale is used to harmonize results from different thromboplastins for patients on vitamin K antagonists, but its use in other clinical settings is limited 2
Interpretation of Test Results
- Abnormal PT and APTT results can pose a diagnostic dilemma, and a practical approach to evaluation is necessary 3
- Isolated prolongation of APTT may result from low levels of factors VIII, IX, or XI, while a slightly prolonged APTT and moderate decrease in factor VIII may indicate von Willebrand disease or hemophilia A 4
- A greatly prolonged APTT and very low levels of factor VIII can result from an acquired factor VIII inhibitor or severe von Willebrand disease 4
Clinical Evaluation of Bleeding and Bruising
- The patient history and physical examination findings can help determine the underlying cause of bleeding or bruising 5
- Initial laboratory testing includes a complete blood count, peripheral blood smear, PT, and PTT, with further testing guided by the results 5
- A normal PT and prolonged PTT may indicate a deficit in the intrinsic pathway, while a vitamin K challenge is indicated in patients with an abnormal PT and normal PTT 5
Postoperative Changes in Procoagulant Factors
- Surgical patients develop hypercoagulability after surgery, with changes in procoagulant factors and increased risk of thrombotic events 6
- PT and APTT may not reliably reflect the hypercoagulatory state, and other tests such as thrombelastometry and multiplate electrode aggregometry may be necessary 6