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A Primer on Effectiveness and Efficacy Trials

Singal, Amit G MD, MS1,2; Higgins, Peter D R MD, PhD3; Waljee, Akbar K MD, MS3,4

Clinical and Translational Gastroenterology: January 2014 - Volume 5 - Issue 1 - p e45
doi: 10.1038/ctg.2013.13
Clinical/Narrative Review: PDF Only

Although efficacy and effectiveness studies are both important when evaluating interventions, they serve distinct purposes and have different study designs. Unfortunately, the distinction between these two types of trials is often poorly understood. In this primer, we highlight several differences between these two types of trials including study design, patient populations, intervention design, data analysis, and result reporting.

1Department of Internal Medicine, UT Southwestern Medical Center, Dallas, Texas, USA

2Department of Clinical Sciences, University of Texas Southwestern, Dallas, Texas, USA

3Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA

4Veterans Affairs Center for Clinical Management Research, Ann Arbor, Michigan, USA

*Correspondence: Amit G. Singal, MD, MS, Dedman Scholar of Clinical Care, Division of Digestive and Liver Diseases, University of Texas Southwestern Medical Center, 5959 Harry Hines Blvd, POB 1, Suite 420, Dallas, Texas 75390-8887, USA. E-mail:

Received 19 June 2013; accepted 19 August 2013

published online 2 January 2014

© 2014 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of The American College of Gastroenterology