Likelihood Ratios

• Probability of a given test result in patients with as opposed to without the disease

  • Fagan nomogram
  • Test/Treatment threshold

• Liatest D-Dimer:

  • Positive LR: 1.5
  • Negative LR: 0.1

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Diagnostic tests tell us nothing about the magnitude by which the test result strengthens the clinical assessment

Derived from sensitivity and specificity

Represents the magnitude of change from the pretest assessment of the probability of disease to the likelihood of disease after knowing the result of a test

L.R. Indicates how much that result will raise or lower the probability of disease