Statistical significance versus clinical importance: trials on exercise therapy for chronic low back pain as example.

STUDY DESIGN. Critical appraisal of the literature. OBJECIVES. The objective of this study was to assess if results of back pain trials are statistically significant and clinically important. SUMMARY OF BACKGROUND DATA. There seems to be a discrepancy between conclusions reported by authors and actual results of randomized controlled trials. Little attention has been paid to the problem of over-reporting of conclusions. METHODS. All 43 trials of the Cochrane review on exercise therapy for low back pain were included. Descriptive analyses were conducted. RESULTS. Eighteen trials reported positive conclusions in favor of exercise. Only six of the 43 studies showed both clinically important and statistically significant differences in favor of the exercise groups on function, and 4 on pain. CONCLUSION. It seems that many conclusions of studies of exercise therapy for chronic low back pain have been based on statistical significance of results rather than on clinical importance and, consequently, may have been too positive. Authors of trials should report not only statistical significance of results but also clinical importance. © 2007 Lippincott Williams & Wilkins, Inc.