Coagulation Testing

Coagulation Testing

David Ray Velez, MD

Table of Contents

Conventional Labs

Bleeding Time

  • Test: A Small Incision is Made in a Standardized Fashion and Time is Recorded Until Bleeding Stops
  • Evaluates: Platelet Function (Adhesion and Aggregation)
    • Not Effected by Coagulation Factor Disorders
  • Normal Time: 1-9 Minutes

Prothrombin Time (PT)

  • Test: Thromboplastin is Added to Plasma and Time is Recorded Until Clot Forms
  • Evaluates: Extrinsic and Common Coagulation Pathway Function
    • Factors II, V, VII, and X
  • The Best Test for Synthetic Liver Function
  • Normal Time: 10-12 Seconds

Partial Thromboplastin Time (PTT)

  • Test: Calcium and Activated Substances (Kaolin and Cephalin) are Added to Plasma and Time is Recorded Until Clot Forms
  • Evaluates: Intrinsic and Common Coagulation Pathway Function
    • All Factors Except VII and XIII
  • Goal for Anticoagulation: 60-100 Seconds
  • Normal Time: 30-45 Seconds

International Normalized Ratio (INR)

  • A Calculated Value from Prothrombin Time (PT)
  • Evaluates: Extrinsic and Common Coagulation Pathway Function
  • Normal INR: 1.0
  • Goal for Anticoagulation: 2.0-3.0
    • May Be Higher for Prosthetic Heart Valves

Activated Clotting Time (ACT)

  • Bedside Test Measuring Time to Clot Formation After Activation by Kaolin or Celite
  • Used to Monitor Intraoperative Coagulation Function During Cases Using High Doses of Heparin
    • May Be Obtained Every 20-30 Minutes During the Case
  • Normal Time: 70-120 Seconds
  • Therapeutic Goals:
    • Dialysis: 160-180 Seconds
    • Vascular Surgery: > 150-200 Seconds
    • CABG: 480-600 Seconds
  • Same as R Time in TEG

Thrombelastogram (TEG)

Thrombelastogram (TEG)