A possible indicator of functional pain: poor pain scale correlation.

We studied correlations of pain measures in patients with either inflammatory bowel disease (IBD), a disease with a clear organic cause, or irritable bowel syndrome (IBS), a functional pain syndrome in which there is little demonstrable pathology. Correlations were determined between measures on the visual analogue scale (VAS) and on the McGill Pain Questionnaire (MPQ). The VAS score and present pain intensity scale (PPI) of the MPQ correlated well in the organic IBD but correlated poorly in the functional IBS. Differences in correlation between the VAS and PPI scores in functional versus organic disease did not appear to be due to altered sensory and affective pain components. This finding is similar to what we observed in our previous study of organic and functional pain syndromes in the musculoskeletal system. Correlations between the other measures are also discussed.