Hemostasis/coagulation assays: Prothrombin time (PT)
This is one of three coagulation/hemostatis assays to measure clotting and is an automated plasma analysis, supporting translational research studies.
The Prothrombin time (PT) assay uses an extrinsic pathway to measure the speed of clotting, including factors for VII, X, V and II.
The International Normalized Ratio (INR) is a standardized equation of measuring (coagulation) time in a blood sample in order to unify the results of prothrombin time (PT) acquired from different laboratories, using different reagents.
By comparing PT tests with a control value (mean value in health) and applying a correction factor specific to the equipment (international sensitivity index, ISI), a standardized value is produced: INR = [PT(test)/PT(control)] ISI.