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BackgroundIn rheumatoid arthritis (RA) and spondyloarthritis (Spa), persistent pain remains challenging. In active disease, diffuse noxious inhibitory controls (assessed through conditioned pain modulation (CPM)) are impaired [1]. Little is known regarding impairment of pain pathways in patients under bMDARD.ObjectivesThe main objective of the RAPID (Rheumatism Pain Inhibitory Descending pathways) study, was to assess descending pain modulation (through CPM paradigm) in patients with active RA or Spa, after introduction of first bDMARD with anti-TNF.MethodsWe included 50 RA and 50 Spa patients with active disease, naïve of bDMARD. We assessed clinical disease variables for patients, together with responses to various psychological questionnaires. All participants underwent QST with the determination of heat and cold pain thresholds (HPT-CPT) on dominant forearm and CPM. CPM paradigm require a conditioning stimulus, here applied to the non-dominant foot (cold circulating bath at 8°C during 1min). Descending pain control was assessed as the change in HPT (in °C) following the conditioning stimulus: the higher the CPM effect, the more efficient the inhibitory control. Patients were followed at 3 and 6 months after TNF inhibitor initiation. At both follow-up visits, clinical monitoring of the rheumatism and repeated thermal QST and CPM.ResultsOne hundred patients were included, 59 women, mean age 45.8 (± 14.6) and mean disease duration 7.93 (± 7.96) years. Due to COVID surge 87 patients initiated an anti-TNF, 74 patients completed the follow-up. At 6 months, 40 patients achieved a good therapeutic response (good EULAR response or ASDAS major improvement), 19 patients had a moderate therapeutic response (moderate EULAR response or clinically important improvement) and 15 patients had no therapeutic response. At the end of follow-up, 51 patients were in remission or low disease activity and 47 patients had a pain intensity <4/10. Thermal pain thresholds did not significantly change during follow-up. Mean HPT was at beaseline 42.35°C (+/- 3.68) and at 6 months 42.17°C (+/- 3.67). Mean CPT was at baseline 13.11°C (+/- 10.04) and at 6 months 12.86°C (+/- 9.45). Conditioned pain modulation was significantly changed during follow-up. Mean CPM effect was at baseline 0.25°C (±2.57), 2.64°C (±2.12) at 3 months and 2.96°C (±2.50) at 6 months. At the end of the 6 months follow-up, mean CPM effect was significantly higher in patients with residual mean pain intensity <4/10 compared to patients with persisting pain ≥ 4/10: 3,25°C (± 2,68) vs 2,47 (± 2,11) (p=0.04).ConclusionAfter TNF inhibitor initiation in active RA or SpA, impaired diffuse noxious inhibitory controls are significantly improved. Apart from their articular efficacy, TNF inhibitor have an action on the central nervous system and pain modulation pathways. In patients with persisting pain under bDMARD, diffuse noxious inhibitory controls are not as efficient as patient without residual pain.Reference[1]Trouvin AP, Simunek A, Coste J, Medkour T, Carvès S, Bouhassira D, Perrot S. Mechanisms of chronic pain in inflammatory rheumatism: the role of descending modulation. Pain. 2022 Aug 3. doi: 10.1097/j.pain.0000000000002745.Figure 1.Acknowledgements:NIL.Disclosure of InterestsNone Declared.