THERMAL PERCEPTION THRESHOLDS - INFLUENCE OF DETERMINATION PARADIGM AND REFERENCE TEMPERATURE

The use of different paradigms and initial skin and thermode reference temperatures in quantitative thermal testing does not allow strict co mparison of results generated from different laboratories. We tested ( a) whether the reproducibility of the method of limits is higher for m easurement of isolated warm and cold thresholds (WT, CT) as compared t o difference limen (DL) thresholds, i.e. values derived from alternati ng warm and cold stimulation, and (b) whether WT-, CT- and DL-threshol ds depend on the value of baseline skin and thermode temperatures. In 20 healthy volunteers WT-, CT-, and DL-thresholds were determined at t he volar wrist using a Somedic-Thermotest. In condition A the baseline thermode temperature was set at 30 degrees C, and in conditions B and C at 35 degrees C; in condition C the tested skin area was also warme d to 35 degrees C prior to the test. The randomized tests were repeate d within 1-8 days. WT-, CT-, and DL-values were reproducible, but DL-v alues were more widely spread than WT and CT. CT variability was lowes t in condition A, and WT variability in condition C. We conclude that DL determination should be abandoned, since CT and WT better different iate normal from abnormal thresholds than the coarse DL-values. We rec ommend the use of the lower baseline thermode temperature (30 degrees C) and elimination of warming of the tested skin area prior to the tes t.