How Do Positive Predictive Value and Negative Predictive Value Relate?
The positive predictive value (PPV) indicates the probability that subjects with a positive screening test truly have the disease. Conversely, the negative predictive value (NPV) indicates the probability that subjects with a negative test truly do not have the disease. These values depend on the prevalence of the disease in the population; a higher prevalence increases the PPV and decreases the NPV. Thus, the interpretation of a positive test result should consider the context of disease prevalence.
