Research Waste in Randomised Control Trials of Spinal Manipulative Therapy for Chronic Low Back Pain: Evidence From Trial Sequential Analysis

BACKGROUND: Chronic low back pain is the leading cause of years lived with disability worldwide. Although spinal manipulation therapy (SMT) is recommended in clinical guidelines and supported by randomised clinical trials (RCTs), systematic review conclusions have not changed despite a growing evidence base. This trial sequential analysis evaluates the extent of research waste in this field by identifying when sufficient evidence had been gathered. METHODS: We report a Trial Sequential Analysis using data from the Cochrane review on SMT. This methodological approach assesses whether statistically significant conclusions can be drawn from accumulating evidence by plotting Z-curve graphs with monitoring boundaries; where the Z-scores' fall indicates the benefit, harm or futility of the intervention. Trial Sequential Analysis estimates a required information size, analogous to optimum sample size in a single trial, based on the data. Our primary analysis explored whether conclusions have been drawn for SMT versus other conservative treatments for pain and functional status at 1 month. RESULTS: We included, 60 RCTs (N = 10,312). For the effect of spinal manipulative therapy versus conservative treatments for pain at 1 month, the futility and information size boundary was crossed in 2004, and in 2002 for functional status. At longer follow-up times, these boundaries were reached at similar dates. CONCLUSIONS: RCTs from as early as 2002 have not added to our understanding of the effectiveness of spinal manipulative therapy for chronic low back pain and functional status and therefore constitutes research waste. Conducting further RCTs in this field without a novel research question should be avoided. SIGNIFICANCE STATEMENT: This important research quantifies research waste in the field of chronic low back pain, a condition affecting billions worldwide. We advocate for trials addressing novel questions to ensure finite resources go towards effective treatments rather than producing redundant evidence; upholding research ethics. Highlighting innovative use of trial sequential analysis will provide a model for visually and quantitatively demonstrating research waste which if utilised across disciplines can ensure research prioritisation, increased production of high-value evidence-based medicine for patients, ultimately improving outcomes.