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Sensitivity and Specificity

 

Sensitivity

Proportion of people with the target disorder who have a positive test. It is used to assist in assessing and selecting a diagnostic test/sign/symptom.

Specificity

Proportion of people without the target disorder who have a negative test. It is used to assist in assessing and selecting a diagnostic test/sign/symptom.

SnNout

When a sign/test/symptom has a high Sensitivity: a Negative result rules out the diagnosis. For example, the sensitivity of a history of ankle swelling for diagnosing ascites is 93%; therefore if a person does not have a history of ankle swelling, it is highly unlikely that the person has ascites.

SpPin

When a sign/test/symptom has a high Specificity; a Positive result rules in the diagnosis. For example , the specificity of a fluid wave for diagnosing ascites is 92%; therefore if a person does have a fluid wave, it rules in the diagnosis of ascites.