Comparison of experimental and acute clinical pain responses in humans as pain phenotypes

This study evaluates the sensitivity of normal subjects (N = 617; 369 women, 248 men) to experimentally induced pain including thermal stimuli and the cold pressor test to delineate individual response patterns and pain phenotypes. A subset of subjects (n = 157; 99 women and 58 men) also underwent standardized oral surgery, and the responses to clinically induced acute inflammatory pain were evaluated. A wide range of pain responses was found in both the experimental and clinical situations. The latency for withdrawal in the cold pressor test exhibited a dichotomous distribution of short and long times. Women exhibited higher responses to cold (P < .001) and thermal stimuli (P < .05) than men. Ethnicity affected pain responses to thermal stimuli ranging from 43degreesC to 47degreesC (P < .05) and cold stimuli (P < .001). However, neither gender nor ethnicity affected pain responses to clinically induced acute inflammatory stimuli. Cross-modality comparisons of responses within experimental pain showed strong correlations (P < .01) but weaker relationships with clinical inflammatory pain. These data suggest that the background factors and characteristics of experimental pain responses differ from those of clinical pain; therefore, experimental pain ratings alone are not sufficient to predict responses to clinically induced acute pain. Perspective: The findings of the present study suggest that investigations of pain phenotypes should take into consideration the subjects' gender and ethnicity and the pain-inducing stimuli. The predictive value of experimental pain for clinically induced pain is weak and not reliable. (C) 2004 by the American Pain Society.