Likelihood ratio

Authors
Affiliations

Doctor of Physical Therapy

B.S. in Kinesiology

Doctor of Physical Therapy

B.A. in Neuroscience

The likelihood ratio is defined as the probability of obtaining a positive test result in a patient with the disease divided by the probability of obtaining a positive test result in a patient without the disease.

Calculation

+LR=(Probability of obtaining a positive test in a patient with the disease)Probability of attaining a positive test in a person without the disease

+LR=Sensitivity1Specificity=(True Positive Rate)(False Positive Rate)

Example
  • Sensitivity: 82%
  • Specificity: 96.3%

+LR=Sensitivity1Specificity=0.8210.963=22.2

Since the +LR is “22.2”, this indicates that a person with the condition is 22.2x more likely to test positive than someone without the disease.

Likelihood ratio vs Sensitivity

The likelihood ratio is defined as the probability of obtaining a positive test result in a patient with the disease divided by the probability of obtaining a positive test result in a patient without the disease.

Sensitivity is the probability of obtaining a positive test result in a patient with the disease.

References

1.
Motulsky H. Intuitive Biostatistics: A Nonmathematical Guide to Statistical Thinking. 4th ed. Oxford University Press; 2018.

Citation

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