Evidence-appraisal glossary
Positive likelihood ratio
How many times more likely a positive test result is in people who have the condition than in people who do not; it equals sensitivity divided by (1 minus specificity).
Also called: LR+, positive LR.
The positive likelihood ratio measures how much a positive result raises the probability of disease, and larger values are better for ruling a condition in. As a rough guide, a value above 10 produces a large, often decisive increase in probability, while a value near 1 barely changes it. Unlike predictive values, the likelihood ratio does not depend on prevalence, so it transfers across settings, but it still must be combined with the pre-test probability to yield a post-test probability.
Read the full Reading the Evidence blog.
This is a plain-language methodology definition for reading research. It is general education, not medical advice.