What labs should be ordered for a broad initial workup of easy bruising?

Laboratory Tests for Initial Workup of Easy Bruising

The initial workup for easy bruising should include complete blood count (CBC), prothrombin time (PT), activated partial thromboplastin time (aPTT), and von Willebrand disease testing (VWF antigen, VWF ristocetin cofactor activity, and factor VIII activity). 1, 2

First-Line Laboratory Tests

Basic Hemostasis Screening

• CBC with platelets and peripheral blood smear to evaluate for thrombocytopenia or abnormal platelet morphology 1, 2
• PT/INR to assess the extrinsic coagulation pathway 1
• aPTT to evaluate the intrinsic coagulation pathway 1
• Fibrinogen level to assess for fibrinogen disorders 1

Von Willebrand Disease Testing

• VWF antigen (VWF:Ag) 1
• VWF ristocetin cofactor activity (VWF:RCo) 1
• Factor VIII coagulant activity (FVIII) 1

Interpretation of Initial Results

• Normal PT and aPTT with persistent bleeding symptoms: Consider platelet function disorder or von Willebrand disease 2, 3
• Normal PT with prolonged aPTT: Suggests intrinsic pathway disorder (hemophilia A or B, factor XI deficiency) 2, 3
• Prolonged PT with normal aPTT: Consider extrinsic pathway disorder or vitamin K deficiency 2, 3
• Prolonged PT and aPTT: Evaluate for liver disease or multiple factor deficiencies 3

Second-Line Laboratory Tests (Based on Initial Results)

For Suspected Platelet Function Disorders

• Platelet aggregation studies if initial screening suggests platelet dysfunction 1, 4
• Evaluation for specific platelet disorders (Bernard Soulier syndrome, Glanzmann thrombasthenia) 1
• Consider testing for antiplatelet antibodies if megathrombocytes are present 4

For Suspected Von Willebrand Disease

• VWF multimer analysis if initial VWD testing shows abnormalities or if ratio of VWF:RCo to VWF:Ag is <0.5-0.7 1

For Suspected Coagulation Factor Deficiencies

• Specific factor assays (VIII, IX, XI, XIII) based on abnormal PT/aPTT patterns 1
• Mixing studies if aPTT is prolonged to distinguish between factor deficiency and inhibitor 3

Special Considerations

For Children

• Consider testing for bone metabolism disorders with:
  • Serum calcium, phosphorus, and alkaline phosphatase 1
  • Parathyroid hormone and 25-hydroxy-vitamin D 1
  • Serum copper and ceruloplasmin 1

For Suspected Connective Tissue Disorders

• Physical examination for joint hypermobility, skin hyperextensibility, and other features of Ehlers-Danlos syndrome 1, 5
• Note that patients with connective tissue disorders often have normal coagulation studies despite easy bruising 5

When to Consider Hematology Referral

• Abnormal initial laboratory testing despite absence of obvious cause 2, 3
• Normal laboratory workup but high clinical suspicion for bleeding disorder 2, 3
• Need for specialized testing such as platelet aggregation studies 1
• Patients with family history of bleeding disorders 3

Common Pitfalls to Avoid

• Relying solely on PT and aPTT to rule out bleeding disorders (will miss von Willebrand disease and mild platelet function disorders) 1
• Failure to consider non-hematologic causes of easy bruising (connective tissue disorders, medication effects, non-accidental trauma) 1, 5
• Not obtaining a thorough bleeding history using a structured assessment tool 1, 3
• Overlooking the need for specific VWD testing in patients with mucocutaneous bleeding despite normal PT/aPTT 1

Remember that a normal PT and aPTT do not exclude significant bleeding disorders, particularly von Willebrand disease and platelet function disorders, which are common causes of easy bruising 1, 3.