Positive predictive value

The positive predictive value (PPV) is the probability that an individual who tests positive for a condition in a diagnostic or screening test actually has the condition (true positives). This may also be called diagnostic precision. This value is influenced by both the sensitivity and specificity of the test itself and the prevalence of the condition in those tested. If the pre-test probability is the same as the prevalence, then the PPV is numerically the same as the post-test probability. PPV is important in the economic modelling of diagnostic tests because it indicates the proportion of those who receive further tests or an intervention who can potentially benefit. Those who test positive without the disease (false negatives) may experience side effects of further tests or receive interventions without benefit. PPV is closely related to the negative predictive value (NPV). In an information retrieval context, PPV refers to the precision of the search strategy.