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Tools for Decision Making Sections
Author Bio
Introduction
Probability Theory
Case Study 1: Patient History
Bayes' Theorem
Currently selected section: Methods for Estimating Pre-test Probability
Estimating Likelihood Ratios
Sensitivity and Specificity
Interpreting Test Results
Calculating Post-test Probabilities
Post-test Probabilities in Clinical Practice
Conclusions: Case Study 1
Part II
Part III
References


Chapter 14: Tools for Decision Making: Methods for Estimating Pre-test Probability
        

The form of Bayes' theorem (post-test odds = pre-test odds x likelihood ratio) is a clue to a great principle:

"The interpretation of new information depends on old information."

Expressed in a medical context, this principle means that the interpretation of a test result depends on the clinical characteristics of the patient that determine the pre-test probability of disease.

Clearly, the estimation of pre-test probability is of central importance in clinical medicine. How does one estimate the pre-test probability? There are three basic methods, which are each described in this section.

Click on any of the methods below. Explore all three to compare your estimate of the patient's probability of ischemic chest pain to the results of using each of these three methods.


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