Coagulation Studies

Question 1

What pathway does PT measure?

Answer 1

Extrinsic

Question 2

Which is used in INR calculation, PT or aPTT?

Answer 2

PT

Question 3

What things can prolong PT AND aPTT?

Answer 3

Liver disease
DIC
Vitamin K deficiency
Warfarin

Question 4

What pathway does aPTT measure?

Answer 4

Intrinsic

Question 5

Is PT specific for any clotting abnormalities?

Answer 5

Not really as factor VII is only factor involved and rarely deficient in isolation

Question 6

What conditions result in a prolonged aPTT but not PT?

Answer 6

Haemophilia A (VIII – X-linked recessive)
Haemophilia B (IX – X-linked recessive)
Haemophilia C (XI – autosomal recessive)
von Willebrands disease

Question 7

Why does Von Willebrand Disease lead to a prolonged aPTT and is this always the case?

Answer 7

vWF Binds to factor VIII (preventing breakdown?)

Not always the case, depends how much factor VIII there is

Question 8

Is the PT raised in Von Willebrand disease?

Answer 8

No

Question 9

Do anticoagulants affect PT or aPTT?

Answer 9

BOTH

All anticoagulants including DOACs, warfarin, heparin, LMWH