A critical review of methods used to determine the smallest worthwhile effect of interventions for low back pain.
OBJECTIVE
To critically and systematically review methods used to estimate the smallest worthwhile effect of interventions for nonspecific low back pain.


METHODS
A 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.


RESULTS
The 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.


CONCLUSIONS
The 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.
The George Institute for Global Health, Missenden Road, NSW 2050, Australia. mferreira@george.org.au
Manuela L
ML
Ferreira
Robert D
RD
Herbert
Paulo H
PH
Ferreira
Jane
J
Latimer
Raymond W
RW
Ostelo
Dafne P
DP
Nascimento
Rob J
RJ
Smeets
D003362:Cost-Benefit Analysis; D003627:Data Interpretation, Statistical; D016206:Databases, Bibliographic; D006801:Humans; D017116:Low Back Pain / Q000628:therapy*; D017063:Outcome Assessment, Health Care / Q000379:methods* / Q000706:statistics & numerical data; D017060:Patient Satisfaction; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data*