Review and recommendationsInterpreting the clinical importance of group differences in chronic pain clinical trials: IMMPACT recommendationsDworkin, Robert H.a,*; Turk, Dennis C.b; McDermott, Michael P.c; Peirce-Sandner, Sarahd; Burke, Laurie B.e; Cowan, Penneyf; Farrar, John T.g; Hertz, Sharone; Raja, Srinivasa N.h; Rappaport, Bob A.e; Rauschkolb, Christinei; Sampaio, CristinajAuthor Information aDepartments of Anesthesiology and Neurology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA bDepartment of Anesthesiology, University of Washington, Seattle, WA, USA cDepartments of Biostatistics and Computational Biology and Neurology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA dDepartment of Anesthesiology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA eUnited States Food and Drug Administration, Bethesda, MD, USA fAmerican Chronic Pain Association, Rocklin, CA, USA gDepartment of Clinical Epidemiology and Biostatistics, University of Pennsylvania, Philadelphia, PA, USA hDepartment of Anesthesiology and Critical Care Medicine, Johns Hopkins University, Baltimore, MD, USA iJohnson & Johnson Pharmaceutical Research & Development LLC, Raritan, NJ, USA jFaculdade de Medicina de Lisboa, Portugal *Corresponding author. Address: Departments of Anesthesiology and Neurology, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Box 604, Rochester, NY 14642, USA. Tel.: +1 585 275 3524; fax: +1 585 473 5007. E-mail address:[email protected] ARTICLE INFO Article history: Received April 28, 2009 Received in revised form June 19, 2009 Accepted August 17, 2009. Pain: December 2009 - Volume 146 - Issue 3 - p 238-244 doi: 10.1016/j.pain.2009.08.019 Buy Metrics Abstract An essential component of the interpretation of results of randomized clinical trials of treatments for chronic pain involves the determination of their clinical importance or meaningfulness. This involves two distinct processes—interpreting the clinical importance of individual patient improvements and the clinical importance of group differences—which are frequently misunderstood. In this article, we first describe the essential differences between the interpretation of the clinical importance of patient improvements and of group differences. We then discuss the factors to consider when evaluating the clinical importance of group differences, which include the results of responder analyses of the primary outcome measure, the treatment effect size compared to available therapies, analyses of secondary efficacy endpoints, the safety and tolerability of treatment, the rapidity of onset and durability of the treatment benefit, convenience, cost, limitations of existing treatments, and other factors. The clinical importance of individual patient improvements can be determined by assessing what patients themselves consider meaningful improvement using well-described methods. In contrast, the clinical meaningfulness of group differences must be determined by a multi-factorial evaluation of the benefits and risks of the treatment and of other available treatments for the condition in light of the primary goals of therapy. Such determinations must be conducted on a case-by-case basis, and are ideally informed by patients and their significant others, clinicians, researchers, statisticians, and representatives of society at large. © 2009 Lippincott Williams & Wilkins, Inc.