Changes in descending pain modulation during anti-TNF therapy. A prospective study in rheumatoid arthritis and spondyloarthritis.

Objective: In rheumatoid arthritis (RA) and spondyloarthritis (SpA), managing persistent pain remains challenging. Little is known regarding impaired pain pathways in these patients and the impact of bDMARDs. The objective of the RAPID (Rheumatism Pain Inhibitory Descending pathways) study was to assess pain thresholds and descending pain modulation in patients with active RA or SpA following introduction of a TNF inhibitor. (TNFi) METHODS: Patients with active disease (50RA and 50SpA), naïve to bDMARD/tsDMARD and starting a TNFi were included. Patients were followed for 6 months after TNFi initiation with clinical, psychological, and pain assessment. At all visits, participants underwent quantitative sensory testing with heat and cold pain thresholds (HPT-CPT) and descending inhibition by conditioned pain modulation (CPM). Descending pain control (CPM effect) was assessed as the change in HPT (°C) following a conditioning stimulus.

Results: Of the 100 patients (59 women, mean age 45.8 ±14.6years), 74 completed the 6-month follow-up. Thermal pain thresholds did not significantly change during follow-up. CPM effect improved significantly during follow-up: 0.25 ±2.57°C (baseline) and 2.96 ±2.50°C at 6months (p<0.001). At the end of follow-up, mean CPM effect was significantly higher in patients without significant pain compared with patients with persistent pain >3/10 (3.25°C ±2.68 vs 2.47°C ±2.11; p=0.04) and in patients achieving remission/low disease activity compared with patients with active rheumatism (3.31°C ±2.68 vs 2.18°C ±1.87; p=0.01).

Conclusion: In active inflammatory rheumatisms, impaired descending pain modulation, but not thermal pain thresholds, is improved after TNFi treatment, suggesting a possible effect of TNFi on central pain modulation.