In trials of physiotherapy for chronic low back pain, clinical relevance is rarely interpreted, with great heterogeneity in the frameworks and thresholds used: a meta-research study.

Questions: How do authors of randomised controlled trials (RCTs) interpret the clinical relevance of the effects of physiotherapy interventions compared with no intervention on pain intensity, physical function and time to recovery in people with chronic low back pain (CLBP)? How can the clinical relevance be re-interpreted based on the available smallest worthwhile effect (SWE) threshold for this comparison? Are the studies in this field adequately powered?

Design: Cross-sectional meta-research study.

Participants: People with CLBP.

Outcome Measures: Pain intensity, physical function and time to recovery.

Results: This review included 23 RCTs with 1,645 participants. Twenty-two and 18 studies were included in the analysis of pain intensity and physical function, respectively. No studies investigated time to recovery. Sixteen studies reported varying thresholds to interpret clinical relevance for physical function and pain intensity. Discrepancies between interpretation using the minimal important difference and SWE values were observed in five studies. Study power ranged from 9% to 98%, with only four studies having a power > 80%.

Conclusion: Little attention is given to the interpretation of clinical relevance in RCTs comparing physiotherapy with no intervention in CLBP, with great heterogeneity in the frameworks and thresholds used. Future trials should inform patients and clinicians on whether the effect of an intervention is large enough to be worthwhile, using a reliable and comprehensive approach like available SWE estimates.

Registration: medRxiv https://doi.org/10.1101/2022.12.14.22283454.