Differing correlations between pain measures in syndromes with or without explicable organic pathology.

We investigated the use of pain measures in chronic pain syndromes with and without explicable organic cause by correlating scores obtained from the Visual Analog Scale and from subscales of the McGill Pain Questionnaire in patients with either inflammatory arthritis or primary fibrositis. We confirmed the finding that patients with fibrositis, despite having significantly less demonstrable pathology, report more pain on a significant number of measures. In patients with arthritis, we observed large positive correlations between scores on different pain measures, supporting the hypothesis that these scores validly measure pain secondary to tissue injury. In the fibrositis group, however, significantly lower correlations, and one even strongly negative, were found between scores on different measures. We suggest that commonly used pain measures which have been shown to be valid to study patients with demonstrable pathology may be less valid for measurement of pain in patients with syndrome such as fibrositis, whose pain may be different or more complex than that of patients with explicable organic basis.