Limitations in the Assessment of Pain Reporting Reliability—Validation of the Focused Analgesia Selection Test

Background Unreliable pain reporting predicts placebo responses in clinical trials and has been documented in chronic pain populations. The thermal Focused Analgesia Selection Test (FAST) quantifies Pain Reporting Reliability (PRR) by assessing consistency when rating repeated thermal stimuli of varying intensities presented in pseudo‐randomized order. However, FAST's validity as a pure measure of reporting reliability remains unclear. Methods We investigated whether PRR derived from the thermal FAST is confounded by individual differences in pain sensitivity (pain and tolerance thresholds), stimuli extending beyond individual pain ranges, and temporal trends. Fifty‐five healthy participants (32 women) completed the thermal FAST protocol comprising 49 stimuli across seven temperatures (43°C–50°C). Results Higher pain thresholds predicted lower PRR ( b = −4.66, 95% HDI [−9.18, −0.07]). Exploratory analysis suggests that rating variability was reduced when stimulation fell outside individual pain ranges (below‐range: b = −8.04, 95% HDI [−11.44, −4.72]; above‐range: b = −4.45, 95% HDI [−7.98, −0.90]). Greater coverage of FAST temperatures by individual pain ranges correlated with higher PRR ( ρ = 0.33). Thermode repositioning to prevent habituation at the stimulation site may have induced acute sensitization at the repositioned site as pain ratings increased by +33 and +19 VAS points at the first two stimuli following repositioning. Excluding these trials improved median PRR by 16% (from R 2 = 0.65 to 0.81). Conclusions PRR derived from the current thermal FAST implementation likely conflates reporting consistency with pain sensitivity, psychophysical range effects, and procedural artifacts and may therefore risk misclassifying pain phenotypes as reporting inconsistencies. We propose methodological refinements, particularly individualized stimulus calibration and optimized repositioning protocols, which should be evaluated in confirmatory studies and chronic pain populations.