Dimensions of "unidimensional" ratings of pain and emotions in patients with chronic musculoskeletal pain.

The use of unidimensional scales to measure pain intensity has been criticised because of the multidimensional nature of pain. We conducted multiple linear regression analyses to determine which dimensions of pain--sensory versus affective--predicted scores on unidimensional scales measuring pain intensity and emotions in 109 Italian women suffering from chronic, non-malignant musculoskeletal pain. We then compared the results with earlier findings in two groups of cancer patients suffering from acute post-operative pain and chronic cancer-related pain, respectively. Age, physical capacity and scores on the multidimensional affect and pain survey (MAPS) were used to predict patients' ratings on one visual analogue scale (VAS) and three numerical rating scales (NRS) measuring pain intensity, anxiety and depressed mood. Unidimensional pain intensity ratings were predicted better from sensory than from affective pain predictors, and the affective predictors made no unique contribution (NRS), or only a very small one (VAS). Both sensory and emotional pain aspects were unique predictors of NRS anxiety and depression. Therefore, in contrast to earlier findings in two different types of cancer patients, in subjects affected by chronic non-malignant musculoskeletal pain, the scores on unidimensional pain intensity scales mainly reflect sensory pain dimensions, supporting the discriminant validity of the NRS and VAS used. However, the patients had some difficulty in distinguishing between sensory and emotional information. For this reason, several unidimensional scales to rate pain intensity and emotions separately should be used to obtain a complete picture of the status and needs of any given patient.