week 4-coagulation testing

Question 1

Why is Ca added to reaction tubes in our routine coagulation tests

Answer 1

Because collection tubes contain citrate. Citrate is a weak Ca chelator and sequesters endogenous Ca in blood and so samples don’t clot unless Ca is added

Question 2

What part of CBC screens for a cause of bleeding

Answer 2

platelet count

Question 3

patient presents with petechiation (small hemorrhages) and has a platelet count in the middle of the ref range. what glycoprotein might be to blame?

Answer 3

vWF

Question 4

majority of coagulation factors are made by liver and circulate the blood as zymogens. What substances must be added back to blood in order to set the coag cascade in motion?

Answer 4

each reaction requires an initiator. For PT test, TF must be added. For APTT test, source of contact activation must be added.
Also require phospholipid and Ca source

Question 5

prothrombin time evaluates primarily a single factor in the extrinsic pathway and common pathway. What is the factor evaluated in PT and not APTT?

Answer 5

Factor VII

Question 6

Which 2 coag proteins evaluated by APTT are associated with bleeding disorders?

Answer 6

Factors VIII and IX

Question 7

if both PT and APTT are prolonged, which factors are implicated as being too low or inactive?

Answer 7

Factors II, VII, IX, and X

Question 8

factor VII has shortest half life. If an animal is progressing towards liver failure, which of the two main tests for secondary coag is likely to be prolongued first

Answer 8

PT

Question 9

what does ACT test

Answer 9

extrinsic, intrinsic, and common pathway
uses diatomaceous earth

Question 10

what does PTT test

Answer 10

extrinsic and common
use ca and TF

Question 11

what does aPTT test

Answer 11

intrinsic and common pathway
Ca and contact activator