What does it mean if a test has a high sensitivity but low specificity?

A test with high sensitivity indicates that it is effective at identifying individuals who have the condition being tested for, which means it has a low rate of false negatives; that is, it is unlikely that individuals with the disease will be missed by the test. In contrast, low specificity suggests that there is a high likelihood of false positives, meaning that individuals without the disease may be incorrectly identified as having it.

In a clinical context, this means that while the test is good at ruling out the disease when the results are negative (due to its high sensitivity), positive results should be interpreted with caution. Such tests are valuable for screening purposes when the priority is to identify as many potential cases as possible, even at the risk of generating some incorrect positives. Therefore, a high chance of false positives arises from the low specificity of the test, leading to potential unnecessary follow-up tests or treatments for individuals who do not actually have the disease.