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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.

 

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Number Needed to Treat

Definition: The number of people who need to be treated over a specific period of time to promote one additional good outcome (or prevent one additional bad outcome). The number needed to treat (NNT) for a treatment can be known only if clinical trials of the treatment have been performed.

Example: For example, a clinical research study compared two anti-ulcer drugs for treating gastroesophageal reflux disease (GERD). It found that for every 10 people treated with drug A, 9 had relief of their symptoms. For every 10 people treated with drug B, 8 had relief of their symptoms. The study concluded that, if 10 people were switched from drug B to drug A, the number who had relief of symptoms would increase from 8 to 9. This means that one more person would obtain relief for every 10 who had the medicine switched (Number Needed to Treat = 10).

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