Represents Prothrombin Time (PT) Ratio that would have been obtained if the primary World Health Organization (WHO) reference thromboplastin (IRP 67/40) had been used to perform the PT test using a manual tilt-tube technique. Normalizes PT Ratio by mathematically considering differences in PT reagents (thromboplastin component). INR is a universal or common scale for reporting PT results. Mathematically the INR is derived from the PT ratio raised to the ISI as an exponential power.
