Clotting Cascade

Question 1

Which clotting factors are Vit K dependent?

Answer 1

Proteases - VII, IX, X, II, APC

Cofactors - Protein S

Question 2

Things that cause a long PT / INR but normal PTT

Answer 2

Low VII, mild deficiency of common pathway, warfarin, low bit K, liver disease

Question 3

Things that cause a long PTT but normal INR

Answer 3

vWD (low VIII)
Low contact factor (low XII –> VERY long aPTT)
Lupus type inhibitor (antiphospholipid Ab)

Question 4

Things that cause prolonged PT / INR and aPTT (common pathway)

Answer 4

Usually an acquired coagulopathy

Liver disease, low vit K, warfarin, DIC, high heparin, thrombin inhibitor

Question 5

What is the thrombin time used for?

Answer 5

Looks for something that is inhibiting thrombin.
Sensitive to low fibrinogen
Overly sensitive to heparin (use aPTT).