Youden Index Calculator
To calculate Youden index enter sensitivity and specificity values as percentages (0-100%) in calculator. Input confusion matrix values: true positives, false negatives, true negatives, and false positives.
For example, enter 85 for sensitivity and 90 for specificity.
The calculator displays index value, test performance metrics, and derived statistics like prevalence and predictive values.
Sensitivity = 85%, Specificity = 90%. Youden Index = (85 / 100) + (90 / 100) – 1 = 0.75.
Youden Index Calculator
| Sensitivity (%) | Specificity (%) | Youden Index (J) |
|---|---|---|
| 90% | 85% | 0.75 |
| 95% | 90% | 0.85 |
| 80% | 70% | 0.50 |
| 50% | 50% | 0.00 |
| 60% | 80% | 0.40 |
| 75% | 90% | 0.65 |
| 85% | 95% | 0.80 |
| 40% | 60% | 0.00 |
| 92% | 88% | 0.80 |
| 98% | 97% | 0.95 |
Youden Index Formula
Youden Index (J) = Sensitivity + Specificity - 1Parameters:
- Sensitivity: True Positive Rate (0-1)
- Specificity: True Negative Rate (0-1)
- Result Range: -1 to +1 (perfect test)
- Test Performance: Sensitivity (%) – True Positive Rate Specificity (%) – True Negative Rate
- Confusion Matrix: True Positives (TP), False Negatives (FN), True Negatives (TN), False Positives (FP)
How to Calculate Youden Index?
To calculate Youden Index, first convert sensitivity and specificity to decimals (divide by 100), then add them together and subtract 1. With 85% sensitivity and 90% specificity, calculate (0.85 + 0.90 – 1) = 0.75 Youden Index.
When evaluating a diagnostic test with 95% sensitivity and 85% specificity, the Youden Index calculation is (0.95 + 0.85 – 1) = 0.80, indicating good test performance.
For a screening test showing 75% sensitivity and 92% specificity, the Youden Index would be (0.75 + 0.92 – 1) = 0.67, suggesting moderate diagnostic accuracy.
A test with 82% sensitivity and 78% specificity, the calculation yields (0.82 + 0.78 – 1) = 0.60, representing fair discriminatory ability.
What is Youden Index?
Youden Index is a statistical measure that evaluates the performance of a diagnostic test. It combines sensitivity and specificity into a single value, ranging from -1 to +1. A value of +1 indicates a perfect test with no false positives or false negatives.