Pre- and post-test probability: Difference between revisions

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Revision as of 23:18, 11 January 2015

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'''Pre-test probability''' and '''post-test probability''' (alternatively spelled pretest and posttest probability) are the [[Subjectivity|subjective]] [[probabilities]] of the presence of a condition (such as a [[disease]]) before and after a [[diagnostic test]], respectively. ''Post-test probability'', in turn, can be ''positive'' or ''negative'', depending on whether the test falls out as a [[positive test]] or a [[negative medical test|negative test]], respectively. In some cases, it is used for the probability of developing the condition of interest in the future.

The subjectivity of the probabilities is based on the fact that, in reality, an individual either has the condition or not (with the probability always being either 0% or 100%), so pre- and post-test probabilities for individuals can rather be regarded as psychological phenomena in the minds of those involved in the [[diagnostics]] at hand.

Test, in this sense, can refer to any [[medical test]] (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 [[Medical test#Indications|indication of medical tests]].