POS0506 TENOSYNOVITIS HAS A HIGH SENSITIVITY FOR EARLY ACPA-POSITIVE AND ACPA-NEGATIVE RA: A LARGE CROSS-SECTIONAL MRI STUDY

Abstract

Background:Clinically evident tenosynovitis can be seen in established Rheumatoid arthritis (RA). Imaging research has recently shown that tenosynovitis at small joints occurs in early RA, contributes to typical RA symptoms (including joint swelling) and is infrequent in healthy controls. Imaging-detectable tenosynovitis is often not recognizable at joint examination, hence its prevalence can therefore be underestimated.Objectives:We hypothesized that if MRI-detectable tenosynovitis is a true RA-feature, the sensitivity for RA is high, in both ACPA-positive and -negative RA, and lower in other diseases that are associated with enthesitis (such as Spondyloarthritis (SpA) and Psoriatic Arthritis (PsA)). So far, no large MRI-study addressed these questions.Methods:Consecutive early arthritis patients (n=1211) from one health-care region underwent contrast-enhanced 1.5T MRI of hand and foot at diagnosis. MRIs were scored for synovitis and tenosynovitis by two readers blinded for clinical data. All included patients with ACPA-positive RA (n=250), ACPA-negative RA (n=282), PsA (n=88), SpA with peripheral arthritis (n=24), reactive arthritis (n=30) and self-limiting undifferentiated arthritis (UA;n=76) were studied. Sensitivity was calculated.Results:The sensitivity of tenosynovitis in RA was 85%; 88% for ACPA-positive RA and 82% for and ACPA-negative RA (p=0.19). The sensitivity for RA was significantly higher than for PsA (65%;p=0.001), SpA (53%;p<0.001), reactive arthritis (36%;p<0.001) and self-limiting UA (42%;p<0.001). The observed sensitivity of MRI-synovitis was 91% in RA and ranged 83-54% in the other groups.Conclusion:MRI-detected tenosynovitis has a high sensitivity for early ACPA-positive and ACPA-negative RA. This supports both juxta-articular (tenosynovitis) and intra-articular synovial involvement is characteristic for RA.Figure 1.Presence of tenosynovitis (in black) in wrist MCPs and MTPs, in rheumatoid arthritis, stratified for ACPA-status and compared to other diseases Legend: RA: Rheumatoïd arthritis; ACPA: anti-citrullinated protein antibodies; UA: undifferentiated arthritisDisclosure of Interests:None declared