Signal detection and threshold measures for chronic back pain patients, chronic illness patients, and cohort controls to radiant heat stimuli.

Three distinct subject populations consisting of 15 chronic low back pain patients, 11 chronic respiratory patients, and 11 nonpatient controls were studied using a standard radiant heat signal detection methodology. Following determination by ascending limits of each subject's stimulus detection and faint pain thresholds, 26 randomized trials at each of five stimulus levels were administered. Subjects rated each stimulus on a 6-point subjective rating scale ranging from no pain to severe pain. Results indicated that the chronic low back pain patients and chronic respiratory patients had higher radiant heat pain thresholds than the controls, and the chronic low back pain patients had a discrimination deficit for mildly painful stimuli. These results fit the predictions of an adaptation model of pain perception in chronic pain patients as opposed to a hypochondriasis model.