DESIGN: A repeated measures 2-group design was used, with subjects divided into "improved" and "non-improved" groups. The external criterion to identify improved and non-improved patients was a 7-point global perceived effect scale.
SUBJECTS: Seventy-five patients with low back pain who had participated in a randomized controlled trial of postsurgical rehabilitation were included in the study.
INTERVENTIONS: All patients completed both a VAS and McGill pain scale to describe their pain over the last 24 hours and a separate VAS to describe their current pain.
MAIN OUTCOME MEASURES: Responsiveness was evaluated by using receiver-operating characteristic curves, with the analysis repeated for a range of cut-off points on the global perceived effect scale. Secondary analyses of responsiveness were provided by the t value for independent change scores and Spearman's rank correlation coefficient (rho).
RESULTS: The study confirmed the results of earlier studies in finding that the VAS was less responsive to clinical change when used to rate current pain in comparison with pain over the last 24 hours. The study found that the VAS was more responsive than the McGill Pain Questionnaire when both instruments were used to rate pain over the last 24 hours.
CONCLUSION: The results of this study suggest that the VAS may be a better tool than the McGill Pain Questionnaire for measuring pain in clinical trials and clinical practice.
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