Negative likelihood ratio
Negative likelihood ratio
The Negative likelihood ratio (NLR) (pronounced: neg-a-tive like-li-hood ray-shio) is a statistical term used in epidemiology and evidence-based medicine. It is a measure of the probability that a test result will be negative when the condition being looked for is present compared to the probability that the test result will be negative when the condition is absent.
Definition
The negative likelihood ratio is defined as the ratio of the probability of a negative test result given the presence of the disease to the probability of a negative test result given the absence of the disease. It is calculated as follows:
- NLR = (1 - Sensitivity) / Specificity
where:
- Sensitivity is the probability that a test result will be positive when the disease is present (true positive rate), and
- Specificity is the probability that a test result will be negative when the disease is absent (true negative rate).
Interpretation
The NLR is used to assess the performance of a diagnostic test. The lower the NLR, the better the test is at ruling out the disease when the test result is negative. An NLR of 1 indicates that the test does not change the probability of having the disease. An NLR less than 1 indicates that the test result being negative makes the disease less likely, while an NLR greater than 1 indicates that the test result being negative makes the disease more likely.
Related terms
- Positive likelihood ratio
- Sensitivity (statistics)
- Specificity (statistics)
- Pre-test probability
- Post-test probability
See also
External links
- Medical encyclopedia article on Negative likelihood ratio
- Wikipedia's article - Negative likelihood ratio
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