📊 Sensitivity / Specificity


Sensitivity, specificity, and likelihood ratios can be tricky concepts to understand and apply. This calculation sheet can help you better understand the meaning behind these terms.

Included in this sheet is a 2x2 table complete with calculations for the following:

Sensitivity

  • The proportion of people WITH the condition who get a (+) test. Also known as the True Positive Rate.

Specificity

  • The proportion of people WITHOUT the condition who get a (-) test. Also known as the True Negative Rate.

Positive Likelihood Ratio

  • How much the odds of the condition increase based on a (+) test

Negative Likelihood Ratio

  • How much the odds of the condition decrease based on a (-) test

Positive Predictive Value

  • If (+) test, the probability of having the condition

Negative Predictive Value

  • If (-) test, the probability of NOT having the condition

Diagnostic Odds Ratio

  • Ratio of odds of (+) test if (+) for condition relative to the odds of (+) if (-) for condition.

Risk Ratio

  • Ratio of the probability of an outcome in an exposed group to the probability of an outcome in an unexposed group.