Measuring Pain in Systemic Sclerosis: Comparison of the Short-form McGill Pain Questionnaire Versus a Single-item Measure of Pain

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.