What should be done for a patient with abnormal Prothrombin Time (PT), Partial Thromboplastin Time (PTT), and International Normalized Ratio (INR) results?

Management of Abnormal PT, PTT, and INR Results

Abnormal coagulation tests (PT, PTT, INR) should be evaluated based on the clinical context, with intervention determined by the underlying cause rather than treating the laboratory value itself. 1

Initial Assessment and Interpretation

• First determine if patient is on anticoagulation therapy:

  • If on vitamin K antagonists (warfarin): INR is specifically designed and validated for monitoring these patients 1, 2
  • If not on anticoagulation: INR has limited validity for general coagulopathy screening 1

• Assess for active bleeding or upcoming procedures:

  • Active bleeding requires more urgent intervention
  • Planned procedures may require correction based on procedure-specific thresholds

Management Algorithm Based on Clinical Context

1. Patients on Warfarin Therapy

• Target INR range: 2.0-3.0 for most indications 2
• INR > 4.0: Provides no additional therapeutic benefit and increases bleeding risk 2
• Monitoring frequency:
  • Daily after initial dose until stable in therapeutic range
  • Then every 1-4 weeks based on stability 2
• Dosage adjustments:
  • Based on PT/INR results
  • Lower doses for elderly, debilitated patients, or those with genetic variations in CYP2C9 and VKORC1 enzymes 2

2. Patients NOT on Anticoagulation Therapy

For Elevated INR < 2.0:

• No intervention needed in absence of bleeding or planned procedures 1
• Plasma transfusion is NOT indicated for INR < 2.0 without active bleeding 1

For Elevated INR > 2.0:

• Fresh Frozen Plasma (FFP) indicated for:
  • Correction of excessive microvascular bleeding with INR > 2.0 1
  • Massive transfusion (>70 ml/kg) when PT/INR cannot be obtained quickly 1
  • Known coagulation factor deficiencies without available specific concentrates 1

For Abnormal PTT:

• Perform routine coagulation assays including aPTT, TT, PT, INR, and anti-Xa levels to assess potential anticoagulant exposure 1
• Consider specialized testing if lupus anticoagulant is suspected 3

Special Considerations

Lupus Anticoagulant

• May cause elevated PTT but typically normal PT 3
• Can cause variability in INR measurements between different laboratory systems 3
• Consider chromogenic factor X assay as alternative monitoring method if INR results seem unreliable 3

Heparin Therapy

• Warfarin may increase aPTT even without heparin 2
• When transitioning from heparin to warfarin:
  • Continue heparin for 4-5 days while starting warfarin
  • Discontinue heparin when desired PT/INR achieved 2
  • Draw blood for PT/INR at least:
    • 5 hours after IV bolus heparin
    • 4 hours after stopping continuous IV heparin
    • 24 hours after subcutaneous heparin 2

Procedural Considerations

• PT/INR determination recommended just before any dental or surgical procedure 2
• For minor procedures: Consider maintaining PT/INR at lower end of therapeutic range 2
• For major procedures: May need to temporarily discontinue warfarin therapy 2

Common Pitfalls to Avoid

1. Treating the number instead of the patient: Correcting mildly abnormal INR (1.0-2.0) with plasma in non-bleeding patients provides no clinical benefit and may cause harm 1

2. Misinterpreting INR in non-warfarin patients: The INR was specifically designed for monitoring vitamin K antagonist therapy, not as a general coagulation screen 1, 4

3. Ignoring pre-analytical variables: Underfilled collection tubes or improper citrate concentration can affect test results 3

4. Overlooking drug interactions: Many medications can affect warfarin metabolism and PT/INR results 2

5. Failing to consider lupus anticoagulant: Can cause variability in INR measurements and potentially misleading results 3

By following this structured approach to abnormal coagulation tests, clinicians can avoid unnecessary interventions while ensuring appropriate management for patients with true coagulation disorders or those requiring anticoagulation monitoring.