Coagulation

Question 1

aPTT

Answer 1

Activated partial thromboplastin time: 30-40 s

• Time it takes to produce fibrin polymeres after adding phospholipids + kaolin + Ca²⁺
• Evaluates the common and intrinsic pathways
• Prolonged in:
  
  • Hemophilia
  • Liver disease
  • Vitamin K deficiency
  • Heparin
  • Transfusion (dilution)
  • DIC
  • Possibly in von Willebrand disease (severe cases of vWD can cause factor VIII deficiency, which leads to an impaired intrinsic pathway)
  • SLE (if lupus anticoagulant is present)
• Monitoring of unfractionated heparin (UFH) therapy

Question 2

PT

Answer 2

Prothrombin time: 10-14 s

• Time it takes to produce fibrin polymeres after adding thromboplastin (a mixture of both phospholipids and tissue factor) + Ca²⁺
• Evaluates the common and extrinsic pathways
• Increased in:
  
  • Vitamin K deficiency
  • Coumarins such as warfarin
  • Transfusion (dilution)
  • Impaired coagulation factor production (e.g., in cirrhosis)
  • Factor VII deficiency
  • DIC
• Monitoring of vitamin K antagonist therapy (e.g. coumarins such as warfarin)

Question 3

INR

Answer 3

International normalized ratio: 0.9-1.3

• Individual’s PT/PT of a control sample

Question 4

TT

Answer 4

Thrombin time: 14-16 s (less than 20 s)

• Time it takes to produce fibrin polymeres after adding thrombin
• Evaluates the common pathway
• Increased in:
  
  • Fibrinogen deficiency
  • DIC
  • Liver disease
  • Heparin
• Monitoring of heparin therapy and fibrinolytic therapy

Question 5

BT

Answer 5

Bleeding time: 3-8 min

Question 6

Platelet count

Answer 6

300000 per µL

Question 7

Fibrinogen level

Answer 7

200-400 mg/dL