The influences of inter-trial interval on the thermal and thermal pain thresholds in quantitative sensory testing.

ABSTRACT

PURPOSE: Thermal threshold and thermal pain threshold determinations are part of quantitative sensory tests. Usually the average of many repeated trials is defined as the threshold. The inter-trial interval (ITI) may have an effect on the later trials. The main purpose of this study was to investigate the influence of ITI on the test results. METHODS: Forty-two healthy subjects were recruited. The limit method was adopted. Each subject received 4 sessions of testing, with one ITI equal to 10, 20, 40 and 60 seconds, respectively. In each session, all four modalities (warm and cold thresholds and cold and hot pain thresholds) were performed. Thermal thresholds were the averages of four trials and thermal pain thresholds were the averages of three trials. The ITI order and the modality order were pseudo-randomized. Analyses of variance were utilized to test the influence of ITI, the modality order and the trial order. RESULTS: The results implied that the test results by the limit method are independent of ITI in the range of 10 to 60 seconds, but the results may not be the true thresholds. CONCLUSION: The results showed that while ITI and the modality order did not have significant effects on the test results, the trial order did have effects on the results of all modalities.