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Glossary of Terms

We know that many of the concepts used on this site can be difficult to understand. For that reason, we have provided you with a glossary to help you make sense of the terms used in Comparative Effectiveness Research. Every word that is defined in this glossary should appear highlighted throughout the Web site. When you come upon a highlighted term and would like to read the full definition, you can either click on the word to visit the glossary or roll your mouse over the word for a pop-up definition.

 

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Likelihood Ratio

Definition:

A measure of the accuracy of a diagnostic test. It is used to determine how likely it is that a person has a specific disease based on test results. When the test result is positive, the likelihood ratio is known as a positive likelihood ratio (LR+). When the test result is negative, the likelihood ratio is known as a negative likelihood ratio (LR-). The likelihood ratio is a way of comparing the probability that the test result would occur in people with the disease as opposed to occurring in people without the disease.

Example:

For example, a diagnostic test called a large core needle biopsy, when used to diagnose breast cancer, has a positive likelihood ratio (LR+) of 16.2 and a negative likelihood ratio (LR-) of 0.03.

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