The Coagulation Panel is a common set of labs ordered to monitor a patient's bleeding status. Lab values are commonly presented in a 3-way diagram, colloquially known as the "Mercedes diagram".
The top left value is the Prothrombin Time (PT). This lab value evaluates the extrinsic pathway and common pathways of coagulation. PT is primarily affected by the following coagulation factors: I (1), II (2), V (5), VII (7), and X (10).
The top right value is the Partial Thromboplastin Time (PTT), sometimes called the activated partial thromboplastin time (aPTT). This lab value evaluates the intrinsic pathway and common pathways of coagulation. PTT is primarily affected by the following coagulation factors: VIII (8), IX (9), XI (11), and XII (12).
The bottom value is the International Normalized Ratio (INR). The INR is a ratio calculated from a patient's PT value, by dividing it by a normal PT value, or population mean. INR is primarily used in patients taking warfarin (Coumadin), to monitor therapeutic dosing.
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