How is the international normalized ratio (INR) calculated given a Control PT of 11.0 seconds and a Patient's PT of 16.5 seconds?

The international normalized ratio (INR) is calculated to standardize prothrombin time (PT) results, enabling comparison across different laboratories and test systems. The formula for calculating INR is:

INR = (Patient's PT / Control PT) ^ ISI

Where ISI is the International Sensitivity Index, which accounts for the sensitivity of a specific thromboplastin. While the ISI value isn't provided in the problem, it is typically a number less than or equal to 1.

In this case, the calculation using the given PT values can be approached as follows:

Firstly, convert the patient's PT and control PT into the INR formula:

1. Divide the patient's PT by the control PT:

16.5 seconds (Patient's PT) / 11.0 seconds (Control PT) = 1.5

2. Raising this value to the power of the ISI (assuming an ISI of 1 for simplicity):

INR = (1.5)^1 = 1.5

This computation indicates that the INR value is derived directly and demonstrates that the patient's coagulation status is elevated compared to the control, which is typical in some clinical scenarios, such as those related to anticoagulation therapy.