Responder index differentiates chronic low back pain treatment effects

A responder index (RI), a composite measurement of face-valid and non-redundant clinical end points that assess aspects of disease, may help resolve some of the challenges associated with the selection and use of appropriate outcome measures for chronic low back pain (LBP). The RI measures response to treatment by specific improvement criteria that differentiate between placebo and active response and establish clinical efficacy.

Bombardier and colleagues tested an established RI that has been validated in 5 clinical trials. A greater than 30% improvement in chronic LBP and patient global assessment (PGA) scores and no worsening (less than 20%) in the Roland Morris Disability Questionnaire total score were the criteria. To study this RI in a trial with an active control, they analyzed data from a 6-week study of celecoxib versus tramadol.

The RI was especially sensitive to the cutoff point used for improvement in the PGA component. In the celecoxib and tramadol arms, 50.7% and 43.7%, respectively, of the patients were classified as responders under the chronic LBP RI. The PGA was the most important component in the RI.

The authors noted that the RI aligns well with recommendations from leading clinical experts and a consensus panel on pain measurement.