The international normalized ratio. A guide to understanding and correcting its problems.

With the increasing use of the international normalized ratio (INR) to monitor warfarin therapy, a number of problems with prothrombin time (PT) testing have been identified that have led some laboratory physicians to question the reliability of the INR. This is ironic, because it was the introduction of the INR system that brought to light some of the long-standing problems with the technique of PT monitoring. However, these problems are not …