What does the International Normalized Ratio measure and what is the typical range?

What does the International Normalized Ratio measure and what is the typical range?

• A. Records the time it takes for a patient to clot; typical range 2.0 - 3.0
• B. Measures platelet count; typical range 150,000 - 450,000
• C. Measures hemoglobin; typical range 12-16 g/dL
• D. Measures white blood cell count; typical range 4-11k

Answer: (A)

INR reflects how long plasma takes to form a clot and, importantly, it standardizes that time so results are comparable across different labs. It measures the extrinsic coagulation pathway and is used mainly to monitor anticoagulant therapy with warfarin. A common therapeutic range for patients on warfarin is about 2.0 to 3.0, balancing the risk of clotting with bleeding. In people not on anticoagulants, normal values are typically around 0.8–1.2. The other options describe different blood tests—platelet count, hemoglobin, and white blood cell count—that assess aspects other than the clotting time measured by INR.

INR reflects how long plasma takes to form a clot and, importantly, it standardizes that time so results are comparable across different labs. It measures the extrinsic coagulation pathway and is used mainly to monitor anticoagulant therapy with warfarin. A common therapeutic range for patients on warfarin is about 2.0 to 3.0, balancing the risk of clotting with bleeding. In people not on anticoagulants, normal values are typically around 0.8–1.2. The other options describe different blood tests—platelet count, hemoglobin, and white blood cell count—that assess aspects other than the clotting time measured by INR.