POS0543 MORNING STIFFNESS IN CLINICALLY SUSPECT ARTHRALGIA IS EXPLAINED BY LOCAL SUBCLINICAL SYNOVITIS AND SYSTEMIC INFLAMMATION
Authors: D. Krijbolder, F. Wouters, E. van Mulligen, A. van der Helm - van Mil
Journal: Annals of the Rheumatic Diseases (2021)

Background: Morning stiffness (MS) is considered a cardinal symptom in the clinical appraisal of arthralgia patients, suggesting presence of subclinical inflammation, which could indicate an increased chance of progression to rheumatoid arthritis (RA). However, the pathophysiology behind MS in arthralgia patients that is clinically suspect for progressing to RA (clinically suspect arthralgia; CSA) has never been studied. In RA, it is presumed that both and local- and systemic inflammation underlie MS. We therefore hypothesize that, in patients with CSA, MS can also be explained by local- and systemic inflammation. Objectives: To determine if MS can be explained by MRI-detected local inflammation (subclinical synovitis and tenosynovitis) and systemic inflammation (C-reactive protein(CRP)). Methods: 514 CSA patients underwent a contrast-enhanced 1.5T MRI of metacarpophalangeal (MCP) 2-5, wrist and metatarsophalangeal (MTP) 1-5 joints, next to clinical assessment and laboratory investigations. MRIs were scored for synovitis and tenosynovitis in line with the RAMRIS-method. MS was dichotomized as present (duration ≥60 minutes) or absent (duration &lt;60 minutes). Associations of MRI-detected synovitis, tenosynovitis and increased CRP with MS were tested with univariable and multivariable logistic regression. Since earlier research in arthritis patients showed that the effect of combined presence of MRI-detected synovitis and tenosynovitis was increased, compared to the effect of these features separately, interaction between MRI-detected synovitis and tenosynovitis, and between synovitis and increased CRP, was assessed. Results: In the studied CSA-patients, mean age was 44 years (sd 13), 397 patients (77%) were female, median tender joint count (TJC-70) was 5 (interquartile range 2-10), and 67 (13%) patients were ACPA-positive. MS was present in 191 (37%) CSA-patients. Baseline characteristics among patients with and without MS were similar. MRI-detected synovitis was more often present in patients with MS compared to patients without MS (34% versus 19%), OR 2.12 (95% CI 1.41-3.19). Also, MRI-detected tenosynovitis was more frequently present in patients with MS (36% versus 24%), OR 1.74 (1.18-2.57). Likewise, increased CRP levels (≥5 mg/L) were more often found in patients with MS (31% versus 18%), OR 2.00 (1.32-3.04). In multivariable analyses, ORs were 1.90 (1.22-2.96) for MRI-detected synovitis and 1.82 (1.18-2.82) for increased CRP. With an OR of 1.20 (0.77-1.87) MRI-detected tenosynovitis was not significantly associated with MS in a multivariable analysis. Interaction between synovitis and tenosynovitis, and between synovitis and CRP was not significant (p-value of 0.13 and 0.15, respectively). Conclusion: Presence of MRI-detected synovitis and increased CRP levels are associated with presence of MS in patients with CSA. This indicates that MS in CSA patients could indeed be induced by both local- and systemic inflammation. Disclosure of Interests: None declared