Pretest probability is defined as the probability of having the condition before a test is applied.

Pretest probability is defined as the probability of having the condition before a test is applied.

• A. Probability after test
• B. Probability during testing
• C. Probability before test
• D. Probability of test failure

Answer: (C)

Pretest probability is the likelihood that a patient has the condition before any diagnostic test results are known. It comes from clinical context, risk factors, symptoms, and how common the disease is in the population. This starting probability is what you update with test results to form the post-test probability. It’s not the probability after testing, nor the probability during testing, and it isn’t about the chance of the test failing (which relates to sensitivity and specificity). In short, it is the probability before the test.

Pretest probability is the likelihood that a patient has the condition before any diagnostic test results are known. It comes from clinical context, risk factors, symptoms, and how common the disease is in the population. This starting probability is what you update with test results to form the post-test probability. It’s not the probability after testing, nor the probability during testing, and it isn’t about the chance of the test failing (which relates to sensitivity and specificity). In short, it is the probability before the test.