Identifying factors that predict who is likely to gain the greatest benefit from different treatments for low back pain is an important research priority. Here we report moderator analyses of the Back Skills Training Trial (BeST) that tested a cognitive-behavioral approach for low back pain.
We recruited 701 participants ages ≥18 years with at least moderately troublesome low back pain present for >6 weeks from 56 general practices in 7 localities across England to a trial adding a group cognitive-behavioral approach to active management advice. The cognitive-behavioral package had a moderate effect on primary outcomes (Roland Morris Disability Questionnaire [RMDQ] and modified Von Korff scales). At 12-month followup, we tested for interaction between randomized groups on 2 prespecified baseline variables (troublesomeness and fear avoidance) and 10 post hoc (exploratory) variables identified from previous studies.
Neither troublesomeness nor fear avoidance moderated treatment effect on any of our primary outcomes. In the final model, the only moderation by baseline variables of the effect of randomization was on the RMDQ outcome. Being younger and currently working both moderated treatment effect, resulting in larger improvements as a response to treatment.
Although BeST is one of the larger trials of back pain treatment, it is still too small to reliably detect moderation if it exists. Since the significant moderation effects were only observed for 1 outcome measure in 3 of 10 post-hoc analyses, we cannot conclude that these are true moderation effects.