Patients with worse disability respond best to cognitive functional therapy for chronic low back pain: a pre-planned secondary analysis of a randomised trial

Question: Do five baseline moderators identify patients with chronic low back pain who respond best to cognitive functional therapy (CFT) when compared with usual care? Design: Secondary analysis of the RESTORE randomised controlled trial. Participants: A total of 492 adults with low back pain for > 3 months with at least moderate pain-related activity limitation. Intervention: Participants were allocated to CFT alone or CFT plus biofeedback; these two groups were combined for this secondary analysis. The control group was usual care. Outcome measures: The outcome was activity limitation measured using the Roland Morris Disability Questionnaire (RMDQ) at 3, 6, 13, 26, 40 and 52 weeks. Investigated effect modifiers were baseline measures of activity limitation, cognitive flexibility, pain intensity, self-efficacy and catastrophising. Results: Baseline levels of activity limitation and, potentially, cognitive flexibility were associated with different effects of CFT treatment, while pain intensity, self-efficacy and catastrophising were not. Patients who had higher baseline activity limitation had greater treatment effects at 13 and 52 weeks. A person with a baseline RMDQ score of 18 (90th percentile) would on average be 6.1 (95% CI 4.8 to 7.4) points better at 13 weeks if they received CFT compared with usual care. However, a person with a baseline score of 7 (10th percentile) would on average be 3.6 (95% CI 2.6 to 4.6) points better at 13 weeks. Conclusion: The finding that CFT is most effective among patients who are most disabled and incur the greatest burden strongly suggests that CFT should be considered as a treatment for this group of patients. Registration: ACTRN12618001396213.