Reproducibility and influence of test modality order on thermal perception and thermal pain thresholds in quantitative sensory testing.

OBJECTIVE: To evaluate the reproducibility of quantitative sensory testing (QST), performed with the method-of-limits (MLI) at different test intervals, by assessing the inter- and intra-individual variation of thermal cold (CT) and warm (WT) perception thresholds, and of thermal cold- (CPT) and heat pain (HPT) thresholds.

METHODS: QST with the MLI was performed in 38 healthy subjects in three repeated and pseudo-randomized test sessions, done at three occasions (days 1, 2 and 7).

RESULTS: At repeated testing, none of the thermal threshold estimates showed systematic significant differences, neither between days nor between sessions within the same day, when determined as first tests (FT), and for CT and WT also after thermal pain assessment (aTPA). However, when determined directly aTPA, both CT and WT were noted significantly higher. Also the coefficients of variation and repeatability showed increased values aTPA.

CONCLUSIONS: The high reproducibility show that the MLI is a feasible method for thermal QST, with reproducible results both at shorter and longer test intervals, on condition that temperature thresholds are determined before any painful thermal stimuli are given, as the latter influence both CT and WT assessments.

SIGNIFICANCE: The findings show that QST with the MLI is a reliable tool for indirect evaluation of human small nerve fiber function.