What is the predictive value of a positive test result?

The predictive value of a positive test result refers to the likelihood that when a test returns a positive result, the disease it is testing for is truly present in the individual. This value goes beyond merely knowing how many positive results there are (which is what the rate of true positives would indicate) and focuses specifically on the accuracy of those results in identifying the presence of the disease.

In practical terms, this predictive value takes into account both the true positives (individuals who have the disease and test positive) and false positives (individuals who do not have the disease but still test positive). A high predictive value means that a positive test result is a reliable indicator of the disease’s presence, enhancing the test's overall effectiveness in diagnosis and clinical decision-making.