Normal Reference Ranges
Adult
PT: 11 - 13.5 sec | INR: 0.8 - 1.1 seconds / ratio
Pediatric
Similar to adults seconds / ratio
Clinical Significance
Measures extrinsic coagulation pathway. INR is used to standardize PT and monitor Warfarin therapy (Target usually 2.0-3.0).
Causes of High
- Warfarin therapy
- Liver failure
- Vitamin K deficiency
- DIC
Causes of Low
- Not clinically significant
- Excess Vitamin K intake (if on Warfarin)