A validation model for verbal description scaling of human clinical pain

Twenty-nine subjects used quantified verbal descriptors of sensory intensity (i.e., weak, mild, intense) or unpleasantness (i.e., annoying, unpleasant, distressing) to assess the intensity or unpleasantness of sensations evoked by painful electrical stimulation of the tooth pulp over a broad stimulus range, and by a natural thermal tooth pulp stimulus, cold spray applied to exposed dentin. In addition, subjects matched the intensity or unpleasantness of the sensations evoked by the natural stimulus to that of the electrical stimuli by both the Method of Limits and the Method of Constant Stimuli. Quantified verbal descriptor values of either the sensory intensity or unpleasantness of the electrical stimuli were linearly related to stimulus intensity on a log scale, indicating that the relationships can be described by power functions. The quantified verbal description of the natural thermal stimulus and the intensity of the electrical stimulus directly matched to the thermal stimulus determined the coordinates of the clinical stimulus data point. This point was close to the experimental stimulus power function, indicating that the verbal magnitude of the clinical stimulus is predicted by the verbal magnitude of the specific electrical stimulus intensity that was matched to the clinical stimulus. This consistency supports the validity of the use of quantified verbal descriptors for the assessment of both experimentally controlled noxious stimulation and uncontrolled clinical pain sensations. It also supports the validity of direct matches between clinical and experimental pain sensations and the unpleasantness of these sensations. This procedure provides a useful independent validational paradigm for clinical pain assessment.