Pre- and post-test probability

Pre-test probability and post-test probability (alternatively spelled pretest and posttest probability) are the <a href="/facts/Probabilities/fgYvMhwb">probabilities</a> of the presence of a condition (such as a <a href="/facts/Disease/55eeQlGL">disease</a>) before and after a <a href="/facts/Diagnostic_test/rRgnuQSD">diagnostic test</a>, respectively. Post-test probability, in turn, can be positive or negative, depending on whether the test falls out as a <a href="/facts/Positive_test/rRgnuQSD">positive test or a negative test</a>, respectively. In some cases, it is used for the probability of developing the condition of interest in the future.
Test, in this sense, can refer to any <a href="/facts/Medical_test/rRgnuQSD">medical test</a> (but usually in the sense of diagnostic tests), and in a broad sense also including questions and even assumptions (such as assuming that the target individual is a female or male). The ability to make a difference between pre- and post-test probabilities of various conditions is a major factor in the <a href="/facts/Medical_test/rRgnuQSD">indication of medical tests</a>.

Pre- and post-test probability open-in-new

Pre- and post-test probability