From the Guidelines
For a patient with bruising, I recommend ordering a complete blood count (CBC), prothrombin time (PT), activated partial thromboplastin time (aPTT), international normalized ratio (INR), fibrinogen level, and platelet function tests, as these are essential in identifying the underlying cause of bruising, which could range from platelet disorders and coagulation factor deficiencies to liver disease or medication effects, as suggested by 1. When evaluating a patient with bruising, it is crucial to consider the clinical history, including medication use, family history of bleeding disorders, and pattern of bruising, to guide which tests are prioritized.
- The CBC evaluates platelet count and can detect thrombocytopenia,
- while PT, aPTT, and INR assess the extrinsic and intrinsic coagulation pathways,
- and fibrinogen levels help evaluate clot formation capability. Additional useful tests include liver function tests, vitamin K levels, and von Willebrand factor assay, as mentioned in 1. If there's suspicion of more severe bleeding disorders, consider factor assays (particularly factors VIII, IX, and XIII), as these can help identify specific coagulation factor deficiencies. The clinical evaluation, including physical examination, should also focus on findings that may suggest other causes of increased bleeding, such as evidence of liver disease, splenomegaly, joint and skin laxity, telangiectasia, signs of anemia, or anatomic lesions on gynecologic examination, as outlined in 1. It is also important to note that the history and clinical evaluation can be used to determine the necessity of an evaluation for a possible bleeding disorder, and prevalence and known clinical presentations of individual bleeding disorders can be used to guide the extent of the laboratory testing, as suggested by 1.
From the Research
Laboratory Tests for Bruising
The following laboratory tests are recommended for evaluating bruising:
- Complete blood count (CBC) 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
- Normal PT and PTT results may indicate a platelet disorder 2, 3
- Normal PT result with a prolonged PTT result indicates a disorder of the intrinsic coagulation pathway 3
- Prolonged PT result with a normal PTT result may indicate a disorder of the extrinsic coagulation pathway 3
- A vitamin K challenge is indicated in patients with an abnormal PT and normal PTT 2
- A workup for liver failure is warranted in patients with prolonged PT and PTT 2