# Purpose of wedge product in INR calculation?

What purpose does the wedge product symbol serve in the formula for calculating a patient's international normalized ratio (INR) for managing warfarin doses?

The formula is:

$INR=(PT/MNPT)\wedge ISI$

INR = international normalized ratio PT = prothrombin time MNPT = mean normal prothrombin time ISI = international sensitivity index

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Apparently it is exponentiation, compare

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Calculate the International Normalized Ratio using the numbers above as an example. INR=(patient PT/MNPT)^ ISI = (15.2 s/13.1 s)^1.297=1.213. Note: Normal INR should be between 0.8 and 1.3 Low values of INR (less than 0.5 ) indicate a high risk of a clot, while high values (3 to 5) are associated with risk of bleeding.

Read more: How to Calculate INR | eHow.com http://www.ehow.com/how_5108528_calculate-inr.html#ixzz2790CNQ5o

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So, numerically, $$15.2 / 13.1 \approx 1.1603,$$ then $$1.1603^{1.297} \approx 1.213.$$

If you are not sure how to do the exponentiation, you will need to learn something of logarithms. But my calculator has a button to do it in one step.

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