Study design: Systematic review.
Objective: To evaluate the quality, conduct, and reporting of subgroup analyses performed in randomized controlled trials of therapist-delivered interventions for nonspecific low back pain (NSLBP).
Summary of background data: Randomized controlled trials of therapist-delivered interventions for NSLBP to date have, at best, shown small to moderate positive effects. Identifying subgroups is an important research priority. This review evaluates the quality, conduct, and reporting of subgroup analyses performed in the NSLBP literature.
Methods: Multiple electronic databases were searched for randomized controlled trials of therapist-delivered interventions for NSLBP. Of the identified articles, only articles reporting subgroup analyses (confirmatory or exploratory) were included in the final review. Methodological criteria were used to evaluate the quality of subgroup analyses. The quality of conduct and reporting was also evaluated.
Results: Thirty-nine articles were included in the final review. Of these, only 3 (8%) tested hypotheses about moderators (confirmatory findings), 18 (46%) generated hypotheses about moderators to inform future research (exploratory findings), and 18 (46%) provided insufficient findings. The appropriate statistical test for interaction was performed in 27 of the articles, of which 10 reported results from interaction tests, 4 incorrectly reported results within individual subgroups, and the remaining articles reported either P values or nothing at all.
Conclusion: Subgroup analyses performed in NSLBP trials have been severely underpowered, are only able to provide exploratory or insufficient findings, and have rather poor quality of reporting. Using current approaches, few definitive trials of subgrouping in back pain are very likely to be performed. There is a need to develop new approaches to subgroup identification in back pain research.