From the Guidelines
To diagnose acute bleeding, the most important laboratory tests include complete blood count (CBC), coagulation studies (PT/INR, PTT), and type and screen/crossmatch, as recommended by the most recent guidelines 1. These tests are crucial in assessing the severity of blood loss and identifying potential clotting abnormalities that may be contributing to the bleeding.
- A CBC will reveal hemoglobin and hematocrit levels to assess blood loss severity, while platelet count helps evaluate if thrombocytopenia is contributing to bleeding.
- Coagulation studies identify clotting abnormalities that may cause or worsen bleeding, with PT/INR evaluating the extrinsic pathway and warfarin effect, and PTT assessing the intrinsic pathway and heparin effect.
- Type and screen/crossmatch should be ordered if blood transfusion is anticipated. Additional useful tests include fibrinogen levels and D-dimer to assess for disseminated intravascular coagulation, liver function tests to identify liver-related coagulopathy, and BUN/creatinine to evaluate kidney function and potential uremic bleeding, as suggested by previous studies 1. In specific cases, specialized tests like thromboelastography (TEG) or rotational thromboelastometry (ROTEM) provide real-time assessment of clot formation and stability, and point-of-care hemoglobin measurement can provide rapid results in emergency situations, as noted in the latest research 1. These tests help identify the cause of bleeding and guide appropriate management strategies, ultimately prioritizing morbidity, mortality, and quality of life as the primary outcomes.
From the Research
Laboratory Tests for Diagnosing Acute Bleeding
The following laboratory tests are used to diagnose acute bleeding:
- Bleeding time (BT)
- Platelet count
- Activated partial thromboplastin time (aPTT)
- Prothrombin time (PT)
- Thrombin time (TT) 2
- Complete blood cell count
- Evaluation of a peripheral blood sample 3
Interpretation of Laboratory Test Results
The results of these laboratory tests can be interpreted as follows:
- A low platelet count alone may indicate peripheral destruction of platelets, immunothrombocytopenia, or an abnormality of bone marrow production 2
- An abnormal bleeding time alone may suggest a platelet aggregation defect, often due to medication 2
- An isolated prolongation of the activated partial thromboplastin time may result from low levels of factors VIII, IX, or XI 3
- A prolonged prothrombin time with a normal activated partial thromboplastin time may indicate an abnormal reduction in the vitamin K-dependent clotting factors (II, VII, IX, X) or factor V 2
Additional Tests for Specific Conditions
Additional tests may be ordered to diagnose specific conditions, such as:
- Von Willebrand disease: assays of factor VIII, von Willebrand factor antigen, von Willebrand factor activity, and template bleeding time 3
- Disseminated intravascular coagulation: tests for plasma heparin, hepatopathy, and thrombocytopenia 2
- Liver failure: tests for prolonged PT and PTT 4
Approach to Evaluation of Bleeding and Bruising
The approach to evaluating bleeding and bruising includes:
- Patient history and physical examination to determine the cause of bleeding or bruising 4, 5
- Use of a bleeding assessment tool to indicate possible pathology 4
- Initial laboratory testing, including complete blood count, peripheral blood smear, prothrombin time, and partial thromboplastin time 4, 5
- Referral to a hematologist if initial evaluation indicates a bleeding disorder or if suspicion remains high despite a normal laboratory workup result 4, 5