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The terms "sensitivity" and "specificity" were introduced by American biostatistician Jacob Yerushalmy in 1947. This is especially important when people who are identified as having a condition may be subjected to more testing, expense, stigma, anxiety, etc. This is especially important when the consequence of failing to treat the condition is serious and/or the treatment is very effective and has minimal side effects.Ī test which reliably excludes individuals who do not have the condition, resulting in a high number of true negatives and low number of false positives, will have a high specificity. For all testing, both diagnostic and screening, there is usually a trade-off between sensitivity and specificity, such that higher sensitivities will mean lower specificities and vice versa.Ī test which reliably detects the presence of a condition, resulting in a high number of true positives and low number of false negatives, will have a high sensitivity. If the true status of the condition cannot be known, sensitivity and specificity can be defined relative to a " gold standard test" which is assumed correct. Specificity (true negative rate) is the probability of a negative test result, conditioned on the individual truly being negative.

Sensitivity (true positive rate) is the probability of a positive test result, conditioned on the individual truly being positive.

If individuals who have the condition are considered "positive" and those who don't are considered "negative", then sensitivity is a measure of how well a test can identify true positives and specificity is a measure of how well a test can identify true negatives: Sensitivity and specificity mathematically describe the accuracy of a test which reports the presence or absence of a condition. The circle represents all individuals who tested positive. Sensitivity and specificity - The left half of the image with the solid dots represents individuals who have the condition, while the right half of the image with the hollow dots represents individuals who do not have the condition.