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.

1. First, determine the Sensitivity (true positive rate).
2. Next, determine the Specificity (true negative rate).
3. Next, use the formula YI = Sensitivity + Specificity – 1 to calculate the Youden Index.
4. Finally, calculate the Youden Index.
5. 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