Development and preliminary validation of the focused analgesia selection test to identify accurate pain reporters

Clinical trials of analgesics have been plagued with poor assay sensitivity due, in part, to variability in subjects' pain reporting. Herein, we develop and evaluate the focused analgesia selection test (FAST), a method to measure patients' pain reporting skills. Subjects with osteoarthritis of the hip, knee, and/or ankle with pain intensity of ≥3/10 on a 0-10 numerical rating scale were enrolled. Subjects underwent the FAST procedure, which consists of recording subjects' pain reports in response to repeated administration of thermal noxious stimuli of various intensities applied on the arm with the Medoc® Thermal Sensory Analyzer II. Subjects also rated non-noxious stimuli consisting of visual contrast rating. After performing an exercise task, subjects also rated clinical pain and were asked to report whether their pain had increased, decreased, or stayed the same. Overall, 88 subjects were enrolled, and 83 were included in the analyses. FAST's outcomes including the R2, intraclass correlation coefficient (ICC), and coefficient of variation (CoV) indicated that subjects' pain reporting skills were widely distributed. Higher FAST ICC significantly predicted greater changes in clinical pain following exercise (p=0.017), whereas the visual contrast test did not predict postexercise pain. FAST is the first method that measures subjects' pain reporting skills. Using FAST to enrich clinical trials with "good" pain reporters (with high FAST ICC) could increase assay sensitivity. Further evaluation of FAST is ongoing.