An updated view on the reliability of different protocols for the assessment of conditioned pain modulation
Firstly, Graven-Nielsen et al.1 studied different cuff CPM protocols for their influence on CS intensity, duration, and location at baseline and at 1-month follow-up in 20 pain-free subjects. For TS on the lower leg ICC >0.75 (excellent reliability), for TS on the lower leg in combination with CS on the opposite lower leg ICC >0.75 (excellent reliability), and for the calculated CPM effect ICC >0.6 (good reliability).
Secondly, Imai et al.3 compared 5 different TS modalities (electrical, heat, handheld algometry, cuff pressure pain threshold, and cuff pressure pain tolerance) and 2 different CS (cold pressor test [CPT] and cuff algometry) in 26 pain-free subjects. The study investigated within and between session reliability where sessions were divided by 1 to 3 weeks. The largest CPM effect and the most reliable combination was achieved by handheld algometry as TS and CPT as CS. Reliability for cuff algometry as TS demonstrated ICC >0.75 (excellent reliability) and coefficient of variation (CV) <18%. Moreover, reliability for cuff algometry as TS during cuff CS showed ICC >0.75 (excellent reliability) and CV <18%.
Thirdly, Graven-Nielsen et al.2 investigated CPM in 125 pain-free subjects using the cuff algometry as TS and the CPT as CS. Intersession reliability of cuff algometry demonstrated an ICC >0.75 (excellent reliability) and CV <18%. Further, the study suggested that cuff algometry as TS was not significantly influenced by gender and age.
Finally, Vaegter and Graven-Nielsen5 investigated temporal summation of pain and CPM profiles in 400 patients with chronic pain. Intrasession reliability of cuff algometry as TS showed ICCs >0.75 (excellent reliability) and intrasession CV <19%.
In addition to the impressive work done by Kennedy et al.,4 these recent studies suggest that cuff algometry is a reliable user-independent method for assessing pain sensitivity and CPM in healthy controls and chronic pain patients.