Hematology: Coagulation Testing

Bleeding Time

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

Prothrombin Time (PT)

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

Partial Thromboplastin Time (PTT)

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

International Normalized Ratio (INR)

• Calculated Value from Prothrombin Time (PT)
• Normal INR: 1.0
• Goal for Anticoagulation: 2.0-3.0
  • May Be Higher for Prosthetic Heart Valves
• Relative Contraindications:
  • > 1.5: Surgery
  • > 2.0: Central Line Placement, Percutaneous Bx & Eye Surgery

Activated Clotting Time (ACT)

• Bedside Test Measuring Time to Clot Formation After Activation by Kaolin or Celite
• Used to Monitor Coagulation During Cases Using High Doses of Heparin
  • 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
  • *See Hematology & Oncology: Thrombelastogram (TEG)