What laboratory tests are needed prior to a biopsy?

Laboratory Tests Required Prior to Biopsy

Prior to biopsy, prothrombin time (PT), activated partial thromboplastin time (APTT), and platelet count should be checked to minimize bleeding risk. 1

Essential Pre-Biopsy Laboratory Tests

Coagulation Tests

• Prothrombin time (PT)/INR

  • Relative contraindication if PT ratio >1.4 1
  • For liver biopsies, transvenous approach recommended if INR >1.4 1

• Activated partial thromboplastin time (APTT)

  • Relative contraindication if APTT ratio >1.4 1

• Platelet count

  • Relative contraindication if <100,000/μL 1
  • For liver biopsies, transvenous approach recommended if <50,000/μL 1

Additional Tests Based on Biopsy Type

• For lung biopsies:

  • Pulmonary function tests (spirometry) 1
  • FEV1 <35% predicted requires multidisciplinary team assessment 1

• For liver biopsies:

  • Fibrinogen levels (particularly important if acute kidney injury or decompensated liver disease) 1

Management of Abnormal Results

Anticoagulant Medications

• Oral anticoagulants:

  • Stop at least 4 days before percutaneous lung biopsy 1
  • For liver biopsy, stop 2 days prior (longer for dabigatran depending on renal function) 1

• Aspirin:

  • Consider stopping 3 days prior to liver biopsy when possible 1
  • No strong evidence supporting stopping antiplatelet drugs before lung biopsy 1

Abnormal Coagulation Parameters

• For platelet count <100,000/μL:

  • Consult hematologist before proceeding 1
  • Consider thrombopoietin receptor agonists (TPO-RAs) as alternative to platelet transfusion 1

• For PT/APTT ratio >1.4:

  • Consult hematologist before proceeding 1
  • Fresh frozen plasma (FFP) should NOT be used to correct INR ≤2.0 prior to liver biopsy 1

Special Considerations

High-Risk Patients

• Patients with uraemia, pulmonary hypertension, liver disease, or coagulation disorders require additional assessment 1
• Patients with acute kidney injury or acute/decompensated liver disease should avoid liver biopsy whenever possible 1

Biopsy-Specific Risks

• Pneumothorax is the most common complication of lung biopsy (20.5%), with bleeding complications being less common (haemoptysis 5.3%) 1
• Bleeding risk may be higher in liver biopsies with fibrosis and portal hypertension, even with INR 1.5-2.0 1

Common Pitfalls to Avoid

1. Failing to check coagulation parameters - Even in patients without known bleeding disorders, routine testing is justified to minimize procedural risk 1

2. Inadequate anticoagulant reversal time - Remember warfarin typically takes 4 days to reach INR of 1.5 1

3. Overlooking clinical context - Laboratory values should be interpreted alongside patient's clinical condition, not in isolation 2

4. Unnecessary testing - For musculoskeletal core needle biopsies, evidence suggests low bleeding risk even without preprocedural coagulation testing 3

5. Ignoring vitamin K status - Vitamin K depletion should be corrected before liver biopsy 1

By following these guidelines, clinicians can minimize bleeding complications while ensuring appropriate patient selection for biopsy procedures.