Abstract
Objective. Studies of pain in systemic sclerosis (SSc) have used a variety of measures, including single-item measures and the 15-item short-form McGill Pain Questionnaire (MPQ-SF). The objective of our study was to compare the performance of the MPQ-SF to a single-item pain numerical rating scale (NRS) and determine whether the MPQ-SF effectively differentiates between sensory and affective components of pain in SSc.
Methods. A cross-sectional, multicenter study of 1091 patients from the Canadian Scleroderma Research Group Registry who completed the MPQ-SF and pain NRS. Correlations of MPQ-SF total scores and pain NRS scores with relevant outcome measures (disability, quality of life, depressive symptoms) were compared. To assess whether the MPQ-SF differentiated between sensory and affective factors, confirmatory factor analysis modeling was used, and correlations of sensory and affective factor scores with other outcome measures were compared.
Results. MPQ-SF total score and the pain NRS correlated similarly with other outcome measures, as did the sensory and affective scores. MPQ-SF sensory and affective factors were highly correlated (0.92), and a single-factor model fit as well as a 2-factor (sensory and affective) model.
Conclusion. The substantial overlap between sensory and affective subscales of the MPQ-SF and the similarity of the MPQ-SF and NRS pain measures compared to other patient-reported outcomes suggest that the 15-item MPQ-SF does not provide tangible advantages compared to the single-item pain NRS. These findings support recommendations to use a single-item NRS pain measure in SSc as it is less burdensome to patients than the MPQ-SF.
Footnotes
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Supported by a research grant from the Fonds de la Recherche en Santé Québec (B.D. Thombs) and by an American College of Rheumatology Research and Education Rheumatology Investigator Award (B.D. Thombs). Dr. Baron is the director of the Canadian Scleroderma Research Group, which receives grant funding from the Canadian Institutes of Health Research, the Scleroderma Society of Canada and its provincial chapters, Scleroderma Society of Ontario, Sclérodermie Québec, and the Ontario Arthritis Society, and education grants from Actelion Pharmaceuticals and Pfizer Inc. Drs. Thombs and Hudson are supported by New Investigator Awards from the Canadian Institutes of Health Research and Établissement de Jeunes Chercheurs awards from the Fonds de la Recherche en Santé Québec.
- Accepted for publication July 6, 2011.