# Sensitivity and Specificity Calculator

> Free sensitivity and specificity calculator. Enter a 2x2 table to get sensitivity, specificity, PPV, NPV and likelihood ratios with 95% confidence intervals, a ready-to-paste sentence and R code. Your data never leaves your browser.

Canonical: https://biostatkit.com/sensitivity-specificity

Enter the 2x2 table of an index test against a reference standard and get sensitivity, specificity, predictive values and likelihood ratios with 95% confidence intervals, plus a sentence for your manuscript.

## Methods wording

Sensitivity, specificity, predictive values and accuracy are reported with 95% CIs by the Wilson score method; likelihood ratios with 95% CIs on the log scale (BiostatKit) [1].

Method: Wilson score CIs for proportions, log-method CIs for likelihood ratios.

## Frequently asked questions

### Which confidence interval does this use for sensitivity and specificity?

The Wilson score interval. Some programs use the exact Clopper-Pearson interval, which is slightly wider. Both are acceptable; say which one you used.

### How do I read a likelihood ratio?

LR+ above 10 and LR- below 0.1 are usually considered strong evidence to rule a condition in or out. They do not depend on prevalence; multiply the pre-test odds by the LR to get post-test odds.

### Why do PPV and NPV change with prevalence?

A positive result is more likely to be a true positive when the condition is common. Enter another prevalence in the optional box to see PPV and NPV for another setting.

### What happens with a zero cell?

Likelihood ratios become 0 or infinite. This tool adds 0.5 to every cell for the likelihood ratios and says so; report that choice.

## Related calculators

- [ROC curve and AUC](https://biostatkit.com/roc-auc)
- [Relative risk calculator](https://biostatkit.com/relative-risk)
- [Odds ratio calculator](https://biostatkit.com/odds-ratio)

Author: TS.BS. Vũ Duy Kiên (https://www.vuduykien.com)