The Chiropractic Hospital-Based Interventions Research Outcomes Study: Consistency of Outcomes Between Doctors of Chiropractic Treating Patients With Acute Lower Back Pain

Objective: The aim of this study was to determine if effectiveness differs between community-based doctors of chiropractic administering standardized evidence-based care that includes high-velocity low-amplitude spinal manipulative therapy (SMT) for acute low back pain (LBP).

Methods: A secondary analysis of randomized controlled trial and observational pilot study data was performed with nonrandom allocation to 4 DCs. Patients included those with Quebec Task Force categories less than or equal to 2 and acute LBP of 2 to 4 weeks' duration. The intervention provided was clinical practice guidelines-based care including high-velocity low-amplitude SMT. Primary outcomes included changes from baseline in modified Roland Disability Questionnaire (RDQ) at 24 weeks. Comparisons of simple main effects at 24 weeks and of marginal main effects in repeated-measures analyses were performed.

Results: Between groups, adjusted point-specific differences in RDQ change were minimally clinically important but not statistically significant at 24 weeks (largest pairwise difference, -3.1; 95% confidence interval, -6.3 to 0.1; overall P = .10). However, in optimal analyses that considered the repeated nature of the measurements for each outcome, significant differences in marginal mean RDQ changes were found between groups (largest pairwise difference, -3.8; 95% confidence interval, -4.9 to 2.6; overall P = .03).

Conclusions: Overall, DCs differed modestly in their effectiveness in improving LBP-specific disability. The point estimates mirrored typically reported effect sizes from recent systematic reviews of SMT; however, confidence limits did not exclude clinically negligible effects.