What lab work is recommended for a patient presenting with excessive bruising?

Laboratory Evaluation for Excessive Bruising

The initial laboratory evaluation for patients with excessive bruising should include a complete blood count (CBC) with platelet count, prothrombin time (PT), activated partial thromboplastin time (aPTT), von Willebrand factor antigen (VWF:Ag), von Willebrand factor ristocetin cofactor activity (VWF:RCo), and factor VIII coagulant activity (FVIII). 1

Initial Assessment Algorithm

1. First-line laboratory tests:

   • Complete blood count (CBC) with platelet count
   • Peripheral blood smear
   • Prothrombin time (PT) with INR
   • Activated partial thromboplastin time (aPTT)
   • Fibrinogen level
   • Von Willebrand factor testing (VWF:Ag, VWF:RCo, FVIII)

2. Interpretation of initial results:

   • Normal PT and aPTT: Consider platelet disorders, especially von Willebrand disease (VWD)
   • Normal PT, prolonged aPTT: Suggests intrinsic pathway disorder → perform mixing study
   • Prolonged PT, normal aPTT: Suggests extrinsic pathway disorder → consider vitamin K challenge
   • Prolonged PT and aPTT: Consider liver failure workup or multiple factor deficiencies

Key Clinical Considerations

Pattern Recognition

• Mucocutaneous bleeding (petechiae, epistaxis, gingival bleeding): Suggests platelet dysfunction
• Hemarthroses or deep hematomas: More common in coagulopathy
• Delayed bleeding after trauma or surgery: Characteristic of factor deficiencies

Important Caveats

1. Normal PT and aPTT do not exclude bleeding disorders 1

   • Von Willebrand disease, the most common inherited bleeding disorder, often presents with normal PT and aPTT
   • Specific VWF testing is essential in the initial evaluation

2. Testing limitations 1

   • Medications affecting platelet function should be discontinued 7-10 days before testing
   • Patient factors such as stress, exercise, inflammation, pregnancy, or estrogen use can elevate VWF and FVIII levels, potentially masking disorders
   • ABO blood type and ethnicity influence VWF levels

3. Repeat testing may be necessary 1

   • If initial results are borderline or inconclusive
   • VWD testing should be repeated if initial results are borderline

Follow-up Testing Based on Initial Results

For suspected platelet disorders:

• If initial VWF testing is abnormal: Consider VWF multimer analysis, particularly if VWF:RCo/VWF:Ag ratio is below 0.5-0.7 1
• For suspected platelet function disorders: Consider platelet aggregation studies

For suspected coagulation factor deficiencies:

• Abnormal mixing study: Consider factor assays based on pattern of abnormality
• Prolonged PT with normal aPTT: Consider factor VII deficiency
• Prolonged aPTT with normal PT: Consider factors VIII, IX, XI, or XII deficiencies

Special Populations

Pediatric considerations

• In children with suspicious bruising, always consider both bleeding disorders and non-accidental trauma 2, 1
• Family history is especially important in children who may not have experienced major bleeding episodes

Women with menorrhagia

• Up to 16% of women with menorrhagia and normal gynecological evaluation may have VWD 3
• Additional testing for platelet aggregation and release should follow if VWF testing is normal

When to Refer to Hematology

• When initial testing indicates a bleeding disorder
• When clinical suspicion remains high despite normal initial laboratory workup
• For specialized testing such as:
  • VWF multimer analysis
  • Expanded flow cytometry
  • Thrombin generation assay
  • Clot retraction test
  • Transmission electron microscopy for platelet granule assessment 1

Remember that up to 60-70% of patients with mild-moderate bleeding symptoms may have a bleeding disorder of unknown cause even after initial testing 1, making hematology consultation valuable in cases with high clinical suspicion.