Pre-test probability

Pre-test Probability

Pre-test probability is a fundamental concept in medical diagnostics and evidence-based medicine. It refers to the likelihood that a specific condition or disease is present before a diagnostic test is conducted.

Pronunciation

Pre-test probability: /priː tɛst prɒbəˈbɪlɪti/

Etymology

The term "pre-test probability" is derived from the English words "pre" (before), "test" (examination), and "probability" (likelihood). It was first used in the context of medical statistics and epidemiology to describe the initial likelihood of a disease before further testing.

Definition

Pre-test probability is the probability of a patient having a disease or condition before a diagnostic test is performed. It is based on the patient's medical history, physical examination, and the prevalence of the disease in the relevant population. The pre-test probability helps in interpreting the results of diagnostic tests and in making clinical decisions.

Related Terms

• Post-test probability: The probability of a disease or condition after a diagnostic test has been performed. It is influenced by the pre-test probability and the characteristics of the test, such as its sensitivity and specificity.

• Likelihood ratio: A statistical term that combines the sensitivity and specificity of a test. It is used to adjust the pre-test probability to obtain the post-test probability.

• Bayes' theorem: A theorem in probability theory that describes how to update the probability of a hypothesis based on evidence. It is the mathematical basis for calculating pre-test and post-test probabilities.

• Predictive value: The proportion of patients with positive or negative test results who are correctly diagnosed. It is influenced by the pre-test probability and the characteristics of the test.

See Also

• Diagnostic test
• Medical decision making
• Clinical prediction rule

External links

• Medical encyclopedia article on Pre-test probability
• Wikipedia's article - Pre-test probability

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