Medical Tests: False Positives and Negatives

When a test is performed to detect a disease, there are four possible outcomes.

• If a test indicates that a patient has a disease that the patient does indeed have, this is called a true positive.⁽¹⁾
• However, if the test indicates that a patient has a disease when she does not, it is called a false positive.⁽¹⁾
• If the test indicates the patient is disease-free, and this is indeed the case, it is called a true negative.⁽¹⁾
• Finally, if the test indicates the patient is healthy when in fact the patient has the disease, we call this a false negative.⁽¹⁾

Click on the image below to view a documentary on false positives and negatives.

On the next page you can learn more about medical tests and watch our documentary on sensitivity and specificity.

1. Segen, Joseph C., Wade, Josie."The Patient's Guide to Medical Tests."Infobase Publishing, 2002.