Predictors of clinical pain intensity in patients with fibromyalgia syndrome.

Central changes in pain processing have been previously reported in patients with fibromyalgia syndrome. These changes include decreased thresholds to mechanical and thermal stimuli (allodynia) and central sensitization, both of which are fundamental to the generation of clinical pain. Therefore, psychophysical measures of central pain processing may be useful predictors of clinical pain intensity of fibromyalgia syndrome patients. Previous studies of fibromyalgia syndrome patients have shown statistically significant correlations of psychophysical test results with clinical pain intensity. The tests used to characterize this important relationship were dependent on spinal cord pain mechanisms and included temporal summation of pain or wind-up and wind-up after-sensations. Particularly, the magnitude of wind-up after-sensations appeared to be one of the best predictors for clinical pain intensity of fibromyalgia syndrome patients (27%). Furthermore, the combination of tender point count, negative affect, and wind-up after-sensations accounted for approximately 50% of the variance in clinical pain intensity of fibromyalgia syndrome patients. Therefore, wind-up after-sensations, tender point count, and negative affect not only seem to represent relevant pain mechanisms but also strongly emphasize their importance for fibromyalgia syndrome pain.