Association between Discordance of Disease Activity Indices and Quantitative Sensory Testing Measures of Nociplastic Pain in Patients with Rheumatoid Arthritis.

Objective: This study investigates the association between discordance in commonly collected clinical indicators of rheumatoid arthritis (RA) disease activity and abnormalities in quantitative sensory testing (QST) observed in individuals with nociplastic pain. The goal is to identify low-burden methods of assessing nociplastic pain in rheumatology practice.

Methods: Data from 225 patients with active RA were included for cross-sectional analyses. Measures of discordance in disease activity were: 1) tender swollen joint count difference (TSJD), 2) proportion of subjective components over total DAS28 (DAS28-P), and 3) patient global assessment minus evaluator global assessment (PtGA - EGA). QST measures were pressure pain thresholds (PPT) at the trapezius, temporal summation (TS), and conditioned pain modulation (CPM). We evaluated associations between measures of discordance and QST using unadjusted and multivariable linear regression models.

Results: The mean TSJD was 5.4 (± 8.2), and the mean DAS28-P was 49.7% (± 13.3%). The mean patient global assessment minus evaluator global assessment was 0.7 (± 2.2). Higher TSJD was associated with lower trapezius PPT (β = -0.05, [-0.08, -0.02]) and higher TS (β = 0.29, [0.05, 0.53]). Higher DAS28-P was associated with lower trapezius PPT (β = -0.05 [-0.07, -0.04]) and higher TS (β = 0.21, [0.06, 0.35]). PtGA - EGA was not associated with any QST measures.

Conclusion: Two of our proposed measures of discordance (higher TSJD, DAS28-P) were modestly associated with worse QST measures of nociplastic pain (lower trapezius PPT, higher TS), suggesting that discordance between patient-reported and physician-assessed measures of disease activity may reflect an element of nociplastic pain.