Enter the sensitivity and specificity into the calculator to determine the Youden Index. This calculator can also evaluate any of the variables given the others are known.

## Youden Index Formula

The following formula is used to calculate the Youden Index.

YI = Sensitivity + Specificity - 1

Variables:

- YI is the Youden Index
- Sensitivity is the true positive rate
- Specificity is the true negative rate

To calculate the Youden Index, add the sensitivity and specificity, then subtract 1 from the sum. The Youden Index is a single statistic that captures the performance of a diagnostic test. Its value ranges from -1 to 1, where 1 indicates that there are no false positives or false negatives, -1 indicates that there are only false positives and false negatives, and 0 indicates that the test is not useful.

## What is a Youden Index?

The Youden Index is a single statistic that captures the performance of a diagnostic test. It is defined as the maximum vertical distance between the Receiver Operating Characteristic (ROC) curve and the diagonal or chance line, which represents the performance of a random guess. The Youden Index combines sensitivity and specificity into one number, with a value ranging from 0 to 1. A value of 0 indicates that the test performs no better than chance, while a value of 1 indicates perfect discrimination.

## How to Calculate Youden Index?

The following steps outline how to calculate the Youden Index.

- First, determine the Sensitivity (true positive rate).
- Next, determine the Specificity (true negative rate).
- Next, use the formula YI = Sensitivity + Specificity – 1 to calculate the Youden Index.
- Finally, calculate the Youden Index.
- After inserting the variables and calculating the result, check your answer with the calculator above.

**Example Problem : **

Use the following variables as an example problem to test your knowledge.

Sensitivity (true positive rate) = 0.85

Specificity (true negative rate) = 0.75