A critical review of methods used to determine the smallest worthwhile effect of interventions for low back pain

ObjectiveTo critically and systematically review methods used to estimate the smallest worthwhile effect of interventions for nonspecific low back pain.Study Design and SettingA computerized search was conducted of MEDLINE, CINAHL, LILACS, and EMBASE up to May 2011. Studies were included if they were primary reports intended to measure the smallest worthwhile effect of a health intervention (although they did not need to use this terminology) for nonspecific low back pain.ResultsThe search located 31 studies, which provided a total of 129 estimates of the smallest worthwhile effect. The estimates were given a variety of names, including the Minimum Clinically Important Difference, Minimum Important Difference, Minimum Worthwhile Reductions, and Minimum Important Change. Most estimates were obtained using anchor- or distribution-based methods. These methods are not (or not directly) based on patients’ perceptions, are not intervention-specific, and are not formulated in terms of differences in outcomes with and without intervention.ConclusionThe methods used to estimate the smallest worthwhile effect of interventions for low back pain have important limitations. We recommend that the benefit–harm trade-off method be used to estimate the smallest worthwhile effects of intervention because it overcomes these limitations.