Submitted

Objective: To determine consequences of using different external criteria on responsiveness of the RMDQ in patients with Chronic Low Back Pain. Design: Questionnaire measures before and after rehabilitation treatment, to determine responsiveness. Subjects: Eighty-three patients with non-specific chronic low back pain, referred for treatment. Main measures: The Dutch language version of the Roland Morris Disability Questionnaire (RMDQ-Dv) was used to assess self-reported functional status. The used external criteria were: 1. Global perceived effect of change in complaints. 2. Global perceived effect of change in ability to take care of oneself. 3. Change in rating of pain intensity. 4. Smallest Real Difference (SRD). Standardised response means (SRMs), pooled effect sizes and Receiver Operating Curves were calculated to determine responsiveness and to enable comparison of effect sizes with the thresholds of Cohen. Results: SRMs ranged from 1.33 to 3.45, pooled effect sizes ranged from 1.50 to 2.81, and areas under curves ranged from 0.76 to 1.00, dependent on the used external criterion. Conclusion: Considerable differences were found in responsiveness, when using different external criteria. However, all pooled effect sizes were well above 0.80, and all other statistics were high, indicating good responsiveness of the RMDQ-Dv. Therefore, the RMDQ-Dv is able to distinguish between improved and non-improved patients independent of the used external criterion