From the Guidelines
Laboratory tests for spontaneous bruising should include a complete blood count (CBC) to assess platelet count and morphology, prothrombin time (PT), activated partial thromboplastin time (aPTT), and international normalized ratio (INR) to evaluate clotting function. Additional tests should include a comprehensive metabolic panel to check liver function, vitamin K levels, and tests for von Willebrand disease such as von Willebrand factor antigen and activity 1. If these initial tests are normal but bruising persists, further evaluation may include specialized coagulation tests like factor assays (particularly factors VIII, IX, and XIII), fibrinogen levels, and D-dimer to assess for disseminated intravascular coagulation.
Some key points to consider when evaluating spontaneous bruising include:
- The prevalence of mild platelet disorders is unknown, and testing for mild platelet disorders is challenging 1
- Defects of fibrinogen are rare and can be detected by the fibrinogen concentration and thrombin time 1
- Fibrinolytic defects can cause significant bleeding/bruising but are extremely rare and require specific testing 1
- Medication reviews are essential in elderly patients or those on anticoagulants, as drugs like warfarin, heparin, aspirin, and NSAIDs can increase bruising tendency 1
In terms of the initial screening panel, it should evaluate for conditions with a known prevalence more common than 1 per 500,000 people, including idiopathic thrombocytopenic purpura, all factor deficiencies (except factor XIII deficiency), and VWD 1. The presence of “classic” bleeding symptoms, such as bleeding after circumcision, should also be considered 1.
It's also important to note that many bleeding disorders are rare, and not every child with bruising/bleeding concerning for abuse requires an evaluation for bleeding disorders 1. However, in some instances, bleeding disorders can present in a manner similar to child abuse, and the history and clinical evaluation can be used to determine the necessity of an evaluation for a possible bleeding disorder 1.
From the Research
Laboratory Tests for Spontaneous Bruising
The following laboratory tests are recommended for evaluating spontaneous bruising:
- Complete blood count (CBC) with platelet count 2, 3, 4
- Peripheral blood smear 2, 3, 4
- Prothrombin time (PT) 2, 3, 4
- Partial thromboplastin time (PTT) or activated partial thromboplastin time (aPTT) 2, 3, 4
- International normalized ratio (INR) 3
- Fibrinogen 3
Interpretation of Laboratory Results
- A normal PT and PTT indicate a platelet disorder, such as von Willebrand disease 2
- A normal PT and prolonged PTT signal a deficit in the intrinsic pathway, and a mixing study should be performed 2
- A prolonged PT and normal PTT may indicate a disorder of the extrinsic coagulation pathway 3
- A prolonged PT and PTT may indicate liver failure or a coagulopathy 2