The human body has a complex mechanism that causes blood to clot if a wound occurs – a desirable response under normal circumstances. But under certain clinical conditions, known as thrombotic disorders, this same mechanism can cause an unwanted clot or “thrombus” and is potentially life threatening. Prothrombin Time (PT) is the most common way to express the clotting time of blood. The effectiveness of oral anticoagulants (substances that prevent the clotting of blood) can vary over time – va

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