Rapid Research Review: Sensitivity and Specificity

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An Initiative of the EMRA Research Committee

Terms

Sensitivity: Ability of a test to detect a disease when it is present
Specificity: Ability of a test to detect the absence of a disease

Disease Positive Disease Negative
Test Positive A B
Test Negative C D

Sensitivity= A/(A+C)            Specificity= D/(B+D)

Example: The NEXUS cervical spine rule has been shown to have a sensitivity of between 90-99% and a specificity of 36-38%, depending on the source.

What does this mean?

Sensitivity: The NEXUS criteria will be positive for 90-99% of patients who have a cervical spine injury. (Alternately, the NEXUS criteria will be negative for 1-10% of cervical spine injuries in patients who are injured.)
Specificity: The NEXUS criteria will be negative for 36-38% of patients who do not have a cervical spine fracture. (Alternately, the NEXUS criteria will be positive for 62-64% of patients without a cervical spine injury.)

Extra Point: Do NOT use sensitivity or specificity to predict presence or absence of disease. It should only be used to understand the test’s characteristics.

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