Objective: To investigate the relation between measures of pain threshold and symptoms of distress to determine if fibromyalgia is a discrete construct/ disorder in the clinic.
Methods: 627 patients seen at an outpatient rheumatology centre from 1993 to 1996 underwent tender point and dolorimetry examinations. All completed the assessment scales for fatigue, sleep disturbance, anxiety, depression, global severity, pain, functional disability, and a composite measure of distress constructed from scores of sleep disturbance, fatigue, anxiety, depression, and global severity-the rheumatology distress index (RDI).
Results: In regression analyses, the RDI was linearly related to the count of tender points (r2 = 0.30). Lesser associations were found between the RDI and dolorimetry measurements (r2 = 0.08). The RDI was more strongly correlated with the two measures of pain threshold than any of the individual fibromyalgia symptom variables. In partial correlation analyses, all of the information relating to symptom variables was contained in the tender point count, and dolorimetry was not independently related to symptoms.
Conclusion: Tender points are linearly related to fibromyalgia variables and distress, and there is no discrete enhancement or perturbation of fibromyalgia or distress variables associated with very high levels of tender points. Although fibromyalgia is a recognisable clinical entity, there seems to be no rationale for treating fibromyalgia as a discrete disorder, and it would seem appropriate to consider the entire range of tenderness and distress in clinic patients as well as in research studies. The tender point count functions as a 'sedimentation rate' for distress, and is a better measure than the dolorimetry score.