Objective: To determine the consequences of using different external criteria on responsiveness of the Roland-Morris Disability Questionnaire (RMDQ) in patients with chronic low back pain.
Design: Questionnaire measures before and after rehabilitation treatment.
Setting: Rehabilitation centre.
Subjects: Patients with nonspecific chronic low back pain, referred for treatment.
Main measures: The RMDQ 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. Standardized response means, 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: Standardized response means 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.
Conclusions: All pooled effect sizes were well above 0.80, and all other statistics were high, indicating good responsiveness of the RMDQ. However, considerable differences were found in responsiveness, when using different external criteria in a same study population. Therefore, it can be concluded that the magnitude of the responsiveness statistic depends on the used external criteria.