likelihood ratio ( LR )
Last reviewed 01/2018
- this is defined as the ratio of the probability of a test result among patients with a target disorder to the probability of that same test result among patients who do not have the target disorder
- the likelihood ratio for a positive test is calculated as:
sensitivity / (1-specificity) - the likelihood ratio of a negative result is calculated as:
(1-sensitivity)/specificity
Note that sensitivity = (a/[a+c]) and
specificity = (d/[b+d])
where:
| target disorder present | target disorder absent | |
| test result positive |
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| test result negative |
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