Test-Retest Reliability of Thermal Temporal Summation Using an Individualized Protocol

Temporal summation (TS) refers to the increased perception of pain with repetitive nox- ious stimuli. It is a behavioral correlate of wind-up, the spinal facilitation of recurring C-fiber stimu- lation. In order to utilize TS in clinical pain research, it is important to characterize TS in a wide range of individuals and to establish its test-retest reliability. Building on a fixed-parameter protocol, we developed an individually adjusted protocol to broadly capture thermally generated TS. We then ex- amined the test-retest reliability of TS within-day (intertrial intervals ranging from 2 to 30 minutes) and between-days (intersession interval of 7 days). We generated TS-like effects in 19 of the 21 par- ticipants. Strong correlations were observed across all trials over both days (intraclass correlation (ICC) (A, 10) = .97, 95% confidence level (CL) = .94-.99) and across the initial trials between days (ICC (A, 1) = .83, 95% CL = .58-.93). Repeated measures mixed-effects modeling demonstrated no sig- nificant within-day variation and only a small (5 out of 100 points) between-day variation. Finally, a Bland-Altman analysis suggested that TS is reliable across the range of observed scores. Without intervention, thermally-generated TS is generally stable within day and between days. Perspective: Our study introduces a new strategy to generate thermal TS in a high proportion of individuals. This study confirms the test-retest reliability of thermal TS, supporting its use as a consis- tent behavioral correlate of central nociceptive facilitation.