Research and Communication Unit for Musculoskeletal Health (FORMI), Oslo University Hospital, Oslo, Norway.
Faculty of Medicine, University of Oslo, Oslo, Norway.
Eur J Pain. 2019 Nov;23(10):1879-1889. doi: 10.1002/ejp.1462. Epub 2019 Jul 29.
Assessing conditioning pain modulation (CPM) with spinal reflex measures may produce more objective and stable CPM effects than using psychophysical measures. The aim of the study was to compare the CPM effect and test-retest reliability between a psychophysical protocol with thermal test-stimulus and a spinal reflex protocol with electrical test-stimulus.
Twenty-five healthy volunteers participated in two identical experiments separated by minimum 1 week. The thermal test-stimulus was a constant heat stimulation of 120 s on the subjects' forearm with continuous ratings of pain intensity on a 10 cm visual analogue scale. The electrical test-stimulus was repeated electrical stimulation on the arch of the foot for 120 s, which elicited a nociceptive withdrawal reflex recorded from the anterior tibial muscle. Conditioning stimulus was a 7°C water bath. Differences in the magnitude and test-retest reliability were investigated with repeated-measures analysis of variance and by relative and absolute reliability indices.
The CPM effect was -46% and 4.5% during the thermal and electrical test-stimulus (p < 0.001) respectively. Intraclass correlation coefficient of 0.5 and 0.4 was found with the electrical and thermal test-stimulus respectively. Wide limits of agreement were found for both the electrical (-3.4 to 3.8 mA) and the thermal test-stimulus (-3.2 to 3.6 cm).
More pronounced CPM effect was demonstrated when using a psychophysical protocol with thermal test-stimulus compared to a spinal reflex protocol with electrical test-stimulus. Fair relative reliability and poor absolute reliability (due to high intraindividual variability) was found in both protocols.
The large difference in CPM effect between the two protocols suggests that the CPM effect relates to pain perception rather than nociception on the spinal level. Due to poor absolute intrarater reliability, we recommend caution and further research before using any of the investigated CPM protocols in clinical decision making on an individual level.
使用脊髓反射测量评估条件疼痛调制（CPM）可能会产生比使用心理物理测量更客观和更稳定的 CPM 效应。本研究的目的是比较使用热测试刺激的心理物理方案和使用电测试刺激的脊髓反射方案之间的 CPM 效应和测试-再测试可靠性。
25 名健康志愿者参加了两个完全相同的实验，两次实验之间至少间隔 1 周。热测试刺激是在前臂上用恒定的 120 秒热刺激，用 10 厘米视觉模拟量表连续评定疼痛强度。电测试刺激是对足弓进行重复 120 秒的电刺激，诱发前胫骨肌记录的伤害性撤回反射。条件刺激是 7°C 的水浴。使用重复测量方差分析和相对和绝对可靠性指数研究了幅度和测试-再测试可靠性的差异。
在热和电测试刺激期间，CPM 效应分别为-46%和 4.5%（p<0.001）。电和热测试刺激的组内相关系数分别为 0.5 和 0.4。电（-3.4 至 3.8 mA）和热测试刺激（-3.2 至 3.6 cm）的协议范围都很宽。
与使用电测试刺激的脊髓反射方案相比，使用热测试刺激的心理物理方案显示出更明显的 CPM 效应。两种方案的相对可靠性都很好，但绝对可靠性较差（由于个体内变异性高）。
两种方案之间 CPM 效应的显著差异表明，CPM 效应与疼痛感知有关，而与脊髓水平的伤害感受无关。由于个体内观察者可靠性差，我们建议在临床决策中使用任何一种所研究的 CPM 方案之前，应谨慎并进一步研究。
