INR or PT to monitor Warfarin?

[PokerDoc]

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in a practice test i chose PT and it was wrong and they said it was INR and in the explanation it said

" the World Health Organization (WHO) introduced the INR. This is the ratio of the patient's PT to a control PT that would have been derived by a standard method in which a WHO primary human brain thromboplastin is used. In patients with a history of thrombosis, the INR should be maintained between 2.0 and 3.0. The PT is prolonged when there is a decrease in fibrinogen, factor V, or vitamin K dependent factors (i.e. II, VII, X). The PT is unaffected by a fall in factor X and proteins C and S. Thus, measuring PT (choice B) is inaccurate"


FA says PT though, so now I'm all confused

 

[drizzt3117]

Pt and inr are measuring the same thing, INR is just standardized for tests in all countries.

 

[PokerDoc]

so essentially then it was a bogus question with 2 right answers

 

[nogolfinsnow]

so essentially then it was a bogus question with 2 right answers

INR's really the right answer, because different labs can in theory have different PTs that give you the same INR, so if you're following a patient who gets coags done at multiple labs the INR will give you the real measure of their anticoagulation status.

 

[PokerDoc]

yeah i just looked it up, according to the WHO, INR is the gold standard. It varies among clinician preference in the real world though.

 

[lord_jeebus]

INR is a calculated value derived from PT.

However, as the normal range of PT varies from lab to lab, INR is used to standardize between them, and thus is a constant target for your Coumadin level regardless of who does the test.

EDIT: I see that the above posts say the same thing. Sorry for not reading.