Evidence-appraisal glossary
Negative likelihood ratio
How likely a negative test result is in people who have the condition compared with people who do not; it equals (1 minus sensitivity) divided by specificity.
Also called: LR-, negative LR.
The negative likelihood ratio measures how much a negative result lowers the probability of disease, and smaller values are better for ruling a condition out. As a rough guide, a value below 0.1 produces a large drop in probability, while a value near 1 means a negative result is nearly uninformative. It is prevalence-independent, but a reassuring negative result still leaves meaningful risk when the pre-test probability was high to begin with.
Read the full Reading the Evidence blog.
This is a plain-language methodology definition for reading research. It is general education, not medical advice.