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Pre-test probability and post-test probability (alternatively spelled pretest and posttest probability) are the 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 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 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 indication of medical tests. ==Pre-test probability== The pre-test probability of an individual can be chosen as one of the following: *The prevalence of the disease, which may have to be chosen if no other characteristic is known for the individual, or it can be chosen for ease of calculation even if other characteristics are known although such omission may cause inaccurate results *The post-test probability of the condition resulting from one or more preceding tests *A rough estimation, which may have to be chosen if more systematic approaches are not possible or efficient 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pre- and post-test probability」の詳細全文を読む スポンサード リンク
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