Prothrombin Time and International Normalized Ratio
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Protime, PT, and INR.
To assess and monitor coagulation status related to therapeutic interventions and disorders such as vitamin K deficiency.
Plasma collected in a completely filled blue-top (sodium citrate) tube. If the patient’s hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted.
(Method: Clot detection) 10 to 13 sec.
- International normalized ratio (INR) = 0.9 to 1.1 for patients not receiving anticoagulation therapy; 2 to 3 for patients receiving treatment for venous thrombosis, pulmonary embolism, and valvular heart disease.
- INR = 2.5 to 3.5 for patients with mechanical heart valves and/or receiving treatment for recurrent systemic embolism.
- For patients receiving anticoagulants, therapeutic levels of warfarin are achieved by adjusting the dosage so the prothrombin time (PT) value is 1.5 to 2.5 times longer than normal or so the INR is between 2 and 3.