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: