Pt is prothrombin time
is international normalized ratio, both measure cloting tendency in disease and in health.
In pt each time you need contol which varies place to place and some what unpredictble. So inr solves the problem by uniform standred all over the world. Inr of 2 to 3 if 3 or more means will bleed , under 2 means need more medication ( like coumidine ).