MEASURING CHANGE IN FIBROMYALGIC PAIN - THE RELEVANCE OF PAIN DISTRIBUTION

Objectives: Though being a main characteristic of the syndrome, pain d istribution has seldom been used as outcome measure in fibromyalgia. T he present study aims at comparing the psychometric properties of a pa in distribution measure with the visual analog scale [VAS] on pain, do lorimetry of tender points, and answers from an open-ended question on symptom improvement. Methods: Pain distribution was assessed by a pat ient-made drawing, and quantified using Wallace's ''rule of nine.'' Th e four pain measures were used simultaneously in a repeated measuremen t design to assess treatment response in 48 fibromyalgia patients comp leting four months of either aerobic exercise, stress management or tr eatment-as-usual [control group]. Results: All measures were able to d ifferentiate significantly between treatment and control conditions. A categorical factor analysis showed their change-scores to be valid in the sense that they all measured the same dimension. The open-ended q uestion proved to be the most reliable measure, followed by the pain d rawing and the VAS. The dolorimeter appeared to have considerable meas urement error and low reliability when being used in a repeated measur ement design. Only the pain drawing was significantly related to patie nts' own experience of pain variation, as assessed by the open-ended q uestion. Conclusion: Pain distribution seems to be an appropriate outc ome measure in fibromyalgia, and its use is encouraged in future treat ment research as are the use of an open-ended question and the VAS. Ho wever, the utility of dolorimeter scores from fibromyalgic tender poin ts as a measure to assess change, is questioned.