(104) - Order of heat and pressure tests impacts pain responsivity ratings

Abstract

Considering the volume and variety of trials that use quantitative sensory testing (QST), accounting for potential order effects is imperative when determining the study protocol as well as for accurate data analysis. The present secondary data analyses examined whether the order of two common testing methods (heat and pressure) affected subsequent subjective participant pain ratings. 106 participants (50 females, mean age 30) underwent both thermal pain threshold and tolerance testing and pressure pain threshold testing in randomized order. Thermal pain threshold and tolerance was administered to the right ventral forearm using the Medoc Pathway with a .5 sec/minute rate of rise. Participants indicated when they first felt pain (threshold) and when it became intolerable (tolerance) by pressing a mouse button, which turned the device off. The temperature for each was recorded. Pressure was applied to the left and right trapezius muscle and the left and right thumb joint using an SBMedic algometer. Participants were instructed to say “pain” when they first felt pain as a result of the pressure stimulus. Heat and pressure were measured twice for each area, and an average was calculated for each testing method. T-tests revealed a significant order effect for pressure ratings, such that thermal testing performed first resulted in higher pressure ratings for both the trapezius (P = .013) and thumb (P = .025). Testing order was also significant for heat pain threshold (P = .049) and marginally significant for heat pain tolerance (P = .067), such that performing thermal testing first resulted in higher heat pain temperatures. These data suggest that order of testing impacts overall levels of pain responsivity, particularly in relation to heat and pressure, and could have implications for the interaction of other types of sensory testing (e.g. cold pain tolerance) as well. The current findings speak to the importance of controlling for testing order in QST data.