What is the workup for coagulopathy (coagulation disorder)?

From the Guidelines

A clotting workup should begin with a complete blood count, prothrombin time (PT), activated partial thromboplastin time (aPTT), and fibrinogen level, as recommended by the most recent and highest quality study 1. The initial step in a clotting workup is crucial for identifying potential bleeding or thrombotic disorders.

• A complete blood count (CBC) helps assess platelet count and other blood cell parameters.
• Prothrombin time (PT) and activated partial thromboplastin time (aPTT) are essential for evaluating the coagulation cascade.
• Fibrinogen level is also critical, as it can indicate consumptive coagulopathy or other fibrinogen-related disorders. For patients on anticoagulant therapy, such as direct oral anticoagulants (DOACs), the workup may need to be tailored to the specific anticoagulant used, as different DOACs affect coagulation assays differently 1.
• Dabigatran, a direct thrombin inhibitor, tends to affect the aPTT more than the PT.
• Rivaroxaban, apixaban, and edoxaban, direct FXa inhibitors, impact the PT more than the aPTT. Viscoelastic coagulation tests, such as thromboelastography (TEG) and rotational thromboelastometry (ROTEM), can be useful in detecting coagulopathy associated with DOACs and guiding reversal therapy 1.
• These tests can provide rapid and accurate assessment of coagulation disorders, allowing for prompt decision-making in trauma settings. Proper specimen collection is essential to ensure accurate results, as hemolysis or improper anticoagulant use in collection tubes can affect coagulation assay results 1. The workup should be tailored to the clinical presentation, with bleeding disorders requiring different emphasis than thrombotic conditions, and factor-specific assays may be needed for accurate assessment in patients already on anticoagulants 1.

From the FDA Drug Label

The dosage and administration of warfarin sodium tablets must be individualized for each patient according to the particular patient’s PT/INR response to the drug. The PT reflects the depression of vitamin K dependent Factors VII, X and II. A system of standardizing the PT in oral anticoagulant control was introduced by the World Health Organization in 1983 It is based upon the determination of an International Normalized Ratio (INR) which provides a common basis for communication of PT results and interpretations of therapeutic ranges.

For a clotting workup, the most relevant tests include:

• PT/INR to assess the patient's response to warfarin therapy
• Activated partial thromboplastin time (aPTT) to monitor heparin therapy
• Prothrombin time (PT) to evaluate the depression of vitamin K-dependent factors The dosage of warfarin should be adjusted to maintain a target INR of 2.5 (range, 2.0 to 3.0) for all treatment durations 2. Laboratory control is essential to ensure the patient's INR remains within the therapeutic range, and PT/INR determinations should be done regularly to maintain adequate control 2.

From the Research

Clotting Workup

• The prothrombin time (PT) and activated partial thromboplastin time (APTT) are the most widely used tests to investigate coagulation abnormalities 3.
• These tests are commonly ordered for anticoagulant monitoring, initial evaluation of hemorrhage, and preoperative screening 4.
• Abnormal results from these tests, such as prolonged PT and APTT, may pose a diagnostic dilemma, especially in non-hematological settings 4.

Interpretation of Results

• PT results can be reported as clotting time, percentage activity, PT-ratio, or international normalized ratio (INR) 3.
• APTT results can be reported as clotting time or as a ratio (patient-to-normal clotting time) 3.
• The INR scale is used to harmonize results from different thromboplastins, but its use is limited to patients on treatment with vitamin K antagonists 3.

Predictive Value of Coagulation Tests

• Combined examination of coagulation and fibrinolysis indexes, including PT, APTT, thrombin time, plasma fibrinogen, thrombin-antithrombin complex, and D-dimer, has a high predictive value for deep venous thrombosis (DVT) after proximal femoral nail anti-rotation surgery in elderly patients with femoral intertrochanteric fracture 5.
• Multivariate logistic regression analysis revealed that plasma fibrinogen, thrombin-antithrombin complex, and D-dimer are significantly associated with the development of DVT following surgery 5.