Predictive value of tests

Predictive value of tests is the probability of a target condition (for example a disease) given by the result of a test, often in regard to medical tests.

In cases where a test result makes a binary classification of the test into either a positive or negative test, the resultant predictive value is designated to be a positive predictive value or a negative predictive value, respectively.

In cases where the test result is of a continuous value, the predictive value generally changes continuously along with the value. For example, for a pregnancy test that displays the urine concentration of hCG, the predictive value increases with increasing value of hCG.

A conversion of continuous values into binary values can be performed, such as designating a pregnancy test as "positive" above a certain cutoff value, but this confers a loss of information and generally results in less accurate predictive values.

For more information on conversion and its disadvantages, see Artificial binary classification.