Response across multiple outcomes in a dose-response trial of spinal manipulation for the care of chronic low back pain

Background: The aim of this secondary analysis is to evaluate the effect of dose response of spinal manipulation (SMT) for the treatment of chronic low back pain (cLBP) across multiple domains simultaneously.
Methods: Participants, 400 with cLBP, were randomized to receive 18 sessions of treatment over 6-weeks. Lumbar SMT was performed by a chiropractor at 0, 6, 12, or 18 of the visits, with the other visits providing an attention control. Patients were followed for 52-weeks. Outcomes assessed included unpleasantness, and pain and disability subscales from the modified Von-Korff (MVK) 100-point scale. These outcomes were assessed at 12-weeks, 24-weeks, and across all time points with adjusted linear regression models utilizing generalized estimating equations to account for correlation between multiple outcomes and multiple time points.
Results: Models favored SMT over attention control at 12 weeks and when assessed across all time points. Notably, at 12 weeks, when comparing 12 SMT to 0 SMT, improvement averaged 8.2 points, on a 100 point scale, [95%CI:2.7, 13.8; P=0.004] over pain, unpleasantness, and disability. This beneficial effect was sustained when assessed over all time points with an observed improvement 5.0 [95%CI: 1.0, 8.9; P=0.010]. These results are similar to previous papers showing similar benefit when outcomes were assessed over all time points individually.
Conclusions: Findings from this analysis present an alternative approach to analysis when assessing benefit across multiple domains is of interest. Investigators may want to consider assessing outcomes across multiple domains to better capture the benefit of SMT.