What is the definition of sensitivity in a diagnostic test?

Sensitivity in a diagnostic test is defined as the ability of the test to correctly identify those who have the disease, which is expressed mathematically as the ratio of true positives to the total number of individuals who actually have the disease. This means sensitivity is calculated using the formula:

True positive / (True positive + False negative)

In this context, the numerator represents the cases where the test accurately detects the presence of the disease (true positives), while the denominator accounts for all individuals who truly have the disease, including those for whom the test fails to provide a positive result (false negatives). A high sensitivity indicates that the test is effective at identifying most individuals with the condition, which is crucial for early detection and management of diseases.

This measure is particularly valuable in screening tests, where the goal is to ensure that as few cases of the condition are missed as possible. Understanding sensitivity helps clinicians interpret test results, select appropriate diagnostic approaches, and guide treatment decisions.