Definition
It is the time required for blood to coagulate in vitro under standard conditions.
Methods
- Capillary Tube Method (Normal Range – 8 to 15 minutes)
- Test Tube Method
- Others : aPTT, Prothrombin time, INR
Prothrombin Time
Normal Range – 25 to 30 seconds
Abnormal Prothrombin Time is seen in :
- Haemophilia
- Liver Pathology
- Malabsorption
- Warfarin overdose
International Normalized Ratio
When INR is too high (>4.5) there is increased risk of major haemorrhage as the blood is too thin.
When it is too low (<2.0) there is increased risk of thromboembolism as the blood is very viscous.
– Jainam Shah