By ToolzHive
About this tool
Sensitivity, specificity, PPV, NPV, likelihood ratios and diagnostic odds ratio with CIs.
How to use Diagnostic Accuracy Calculator
- Enter true positives, false positives, false negatives and true negatives.
- Optionally enter the prevalence in the population where the test will be used.
- Read every accuracy measure with its confidence interval.
Worked example
With 90 true positives, 30 false positives, 10 false negatives and 170 true negatives, sensitivity is 90%, specificity 85% and LR+ is 6.0.
Why do PPV and NPV change with prevalence?
Predictive values depend on how common the condition is. The same test has a much lower PPV in screening than in a specialist clinic.
What are good likelihood ratios?
An LR+ above 10 or an LR− below 0.1 changes the probability of disease a lot; values near 1 add little information.
Which confidence interval method is used?
Wilson score intervals for proportions and log-based intervals for ratios, as recommended for diagnostic accuracy studies.
Put this guide into practice
- Diagnostic Accuracy Calculator — Sensitivity, specificity, PPV, NPV, likelihood ratios and diagnostic odds ratio with CIs.