Pain sensitization may contribute to pain severity in rheumatoid arthritis (RA), impacting disease activity assessment. We examined whether pain processing mechanisms were associated with disease activity among RA patients with active disease.
The study included 139 subjects enrolled in the Central Pain in Rheumatoid Arthritis cohort. Subjects underwent quantitative sensory testing (QST), including assessment of pressure pain thresholds (PPTs) at multiple sites, conditioned pain modulation, and temporal summation. RA disease activity was assessed using the Clinical Disease Activity Index (CDAI) and its components. We examined cross-sectional associations between QST measures and disease activity using linear regression.
Low PPTs (high pain sensitization) at all sites were associated with high CDAI scores (P ≤ 0.03) and tender joint counts (P ≤ 0.002). Associations between PPTs and patient global assessments were also seen at most sites. High temporal summation at the forearm (also reflecting high pain sensitization) was significantly associated with high CDAI scores (P = 0.02), patient global assessment scores (P = 0.0006), evaluator global assessment scores (P = 0.01), and tender joint counts (P = 0.02). Conversely, conditioned pain modulation (a measure of descending inhibitory pain pathways) was associated only with tender joint count (P = 0.03).
High pain sensitization is associated with elevations in disease activity measures. Longitudinal studies are underway to elucidate the cause-effect relationships between pain sensitization and inflammatory disease activity in RA.