It makes no significant contribution to the diagnosis or treatment of patients whose PT is prolonged for other reasons. Intensity of Warfarin Therapy in Patients With Double Mechanical Valve or With Additional Risk Factors (mechanical heart valves in both the aortic and mitral position) INR target of 3.0 (range 2.5-3.5) (Grade 2C) Bioprosthetic valve in the mitral position. The INR is used only for patients on stable oral anticoagulant therapy. INR = (Patient’s PT/mean PT of reference range) ISI where: Also used to monitor effects of Warfarin therapy and to study patients with. More sensitive thromboplastins have a low ISI (1.0-1.2), whereas less sensitive thromboplastins have a higher ISI (eg, 2.0-3.0). Prothrombin Time with INR - Screening test for abnormalities of coagulation. In a person who is not taking warfarin, the INR would be approximately 1. Warfarin is prescribed for people with a variety of conditions to thin. In most cases the target INR range will be between 2 and 3, although other ranges may be chosen if there are special circumstances. The PT and INR are used to monitor the effectiveness of the anticoagulant warfarin. The target INR range depends upon the clinical situation. The international sensitivity index (ISI) is an experimentally derived measurement, usually provided by the thromboplastin manufacturer, reflecting thromboplastin (and PT) sensitivity to coagulation deficiencies. The longer it takes the blood to clot in the assay, the higher the PT and INR.

The INR is the ratio of the patient’s PT to the laboratory’s mean normal (reference) PT. The international normalized ratio (INR) is a method of standardizing PT reporting for monitoring the intensity of oral anticoagulant therapy. Critical Findings and Potential Interventions. The PT requires standardization because there are numerous thromboplastins and coagulation testing instruments, and they all vary in their responsiveness to the concentrations or activities of coagulation proteins. INR 2.5 to 3.5 for patients receiving intensive anticoagulation therapy with warfarin. Oral anticoagulants reduce the activities of the 4 vitamin K-dependent procoagulant factors (factors II, VII, IX, and X), and the PT is sensitive to 3 of them. The PT is the most common test used for monitoring oral anticoagulant therapy (warfarin or Coumadin, and congeners). A prolonged PT indicates deficiency of 1 or more coagulation factors (I, II, V, VII, or X) or the presence of a coagulation inhibitor. The prothrombin time (PT) represents the time elapsed between 1) addition of a standardized mixture of tissue thromboplastin and calcium to citrate anticoagulated plasma and 2) detection of clot formation, representing fibrin polymerization resulting from the generation of thrombin, which proteolytically transforms fibrinogen to fibrin.

Pt inr normal range on warfarin