What labs should be ordered to initially assess for an increase in bleeding?

Initial Laboratory Assessment for Increased Bleeding

For initial assessment of increased bleeding, order a complete blood count (CBC) with platelet count, prothrombin time (PT/INR), activated partial thromboplastin time (aPTT), fibrinogen, and D-dimer. 1

Primary Laboratory Panel

The initial laboratory evaluation for a patient with increased bleeding should include:

• Complete Blood Count (CBC) with platelet count

  • Identifies thrombocytopenia (<150 × 10³/μL)
  • Peripheral blood smear examination to exclude pseudothrombocytopenia and identify morphological abnormalities

• Basic Coagulation Tests

  • Prothrombin Time (PT/INR)
  • Activated Partial Thromboplastin Time (aPTT)
  • Fibrinogen level (significant coagulopathy indicated by <2.0 g/L)

• D-dimer

  • Elevated levels (>4000 μg/mL) suggest significant coagulopathy
  • Helps evaluate for consumptive coagulopathy 1

Interpretation of Results

Platelet Abnormalities

• Thrombocytopenia may result from various causes including idiopathic thrombocytopenic purpura, disseminated intravascular coagulation, or medication effects
• Platelet counts <50,000/μL indicate increased bleeding risk
• Platelet counts <20,000/μL with mucous membrane bleeding warrant hospitalization 1

Coagulation Pathway Abnormalities

• Isolated PT prolongation: Suggests factor VII deficiency or vitamin K deficiency
• Isolated aPTT prolongation: May indicate deficiency in factors VIII, IX, or XI
• Both PT and aPTT prolonged: Suggests multiple factor deficiencies, liver disease, or DIC
• Normal PT/aPTT with bleeding: Consider von Willebrand disease or platelet function disorders 1

Additional Testing Based on Initial Results

If initial tests suggest a specific disorder, follow up with:

For Suspected von Willebrand Disease

• von Willebrand factor antigen (VWF:Ag)
• von Willebrand factor activity (VWF:RCo)
• Factor VIII activity (FVIII:C) 1, 2

For Suspected Coagulopathy

• Consider viscoelastic testing (thromboelastometry/ROTEM or thromboelastography/TEG) for faster results and better characterization of coagulopathy 1

Important Considerations and Pitfalls

• Test variability: Different laboratory reagents and instruments can significantly affect PT and aPTT results, potentially leading to different clinical interpretations 3

• Timing matters: D-dimer levels may decrease over time since symptom onset, affecting diagnostic accuracy 1

• Common errors to avoid:

  • Failing to exclude pseudothrombocytopenia
  • Relying solely on platelet count for diagnosis
  • Overlooking medication-induced causes of bleeding
  • Using D-dimer as the sole parameter to guide anticoagulation 1

• Medication review is essential, focusing on anticoagulants, antiplatelet agents, and medications known to affect platelet function (heparin, quinidine/quinine, sulfonamides) 1

Special Populations

Pregnant Patients

• Initial evaluation with proximal compression ultrasound for suspected DVT
• Blood pressure measurement to rule out preeclampsia 1

Patients with Recent Surgery or Trauma

• D-dimer has limited utility due to expected elevation
• Consider viscoelastic testing for more accurate assessment 1

The laboratory evaluation should be guided by clinical presentation, but these initial tests provide a comprehensive framework for assessing increased bleeding risk and directing further diagnostic workup.