Calculate positive and negative likelihood ratios for a diagnostic test.
Likelihood ratios convert a test result into a change in odds, which is why they combine so cleanly with pre-test probability. An LR+ above 10 substantially raises the probability of disease. A test with excellent sensitivity can still be nearly useless if specificity is poor, and the likelihood ratio is what exposes that.
Likelihood Ratio
LR+ = sensitivity ÷ (1 − specificity); post-test odds = pre-test odds × LR
LR+ = sensitivity ÷ (1 − specificity); post-test odds = pre-test odds × LR Likelihood ratios convert a test result into a change in odds, which is why they combine so cleanly with pre-test probability. An LR+ above 10 substantially raises the probability of disease.
A test with excellent sensitivity can still be nearly useless if specificity is poor, and the likelihood ratio is what exposes that.
This calculator takes 3 inputs: Sensitivity, Specificity, Pre-test probability. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.