School of Nursing and Academic Division of Midwifery

RLO: Positive and Negative Predictive Value of Diagnostic Tests

• Introduction
• Tests
• False results
• Prediction table
• Using PPV and NPV
• Assessment
• Feedback
• Resources

In a group of 100 people, 60 have disease, 40 do not have disease. Our ideal test applied to all these people will give 60 positive results in those who have disease and 40 negative results in those without disease. 

In practice tests are not perfect, so not all diseased patients will be picked up by the test. In this case the test gives a positive result in 48 out of the 60 who have disease, therefore 48 are true positive.

© 2006 Graduate Entry Medical School, University of Nottingham

Developer: Caroline Burton

Content author: Elaine Bentley

RLO released: 2nd February, 2007

Page last updated: 23 March, 2021