Study design: Assessment of correlation of measures of low back pain (LBP) using data pooled from 2 identical studies.
Objective: To assess the relative responsiveness of and correlation between various measures of LBP, including the Roland-Morris Disability Questionnaire (RMDQ), the LBP intensity (LBPI) visual analog scale (VAS), and patient's global assessment of response to therapy (PGART).
Summary of background data: Several tools are available to measure pain, functional limitation, and response to therapy for LBP. Studies have shown varying degrees of responsiveness and correlation.
Methods: This was a pooled subgroup analysis of patients with chronic LBP from 2 identical studies comparing etoricoxib 60 mg, 90 mg, and placebo. LBP was assessed by the time-weighted average change from baseline over 12 weeks as measured by RMDQ, LBPI VAS, and PGART. Correlation was calculated using Pearson's correlation coefficient.
Results: The correlation (r) between LBPI and RMDQ changes ranged from 0.657 and 0.703; correlations between LBPI and PGART changes ranged from 0.677 and 0.738. Cutpoints separating responders from nonresponders for all 3 measures fell near the 66.7th percentile of response and were consistent with minimal clinically significant changes identified in the literature.
Conclusion: In this study, the RMDQ, LBPI VAS, and PGART showed a high degree of correlation in measuring response to therapy in LBP, suggesting clinicians may be able to simplify assessments.