POS0741 CLINICALLY UNSUSPECTED JOINT INFLAMMATION DETECTED BY WBMRI IS MORE FREQUENT IN JIA PATIENTS THAN CONTROLS

Abstract

BackgroundWhole-body MRI (WBMRI) enables a comprehensive assessment of joint inflammation in children and young people (CYP) with juvenile idiopathic arthritis (JIA). The clinical relevance of WBMRI-detected inflammation in joints requires further assessment.ObjectivesTo evaluate the frequency of WBMRI-detected subclinical joint inflammation in CYP with JIA and without inflammatory arthritis. To explore the relationship between WBMRI-detected and clinically detected joint inflammation in patients with JIA.MethodsCYP aged 14-24 with JIA (any subtype) or non-inflammatory joint pain (controls) were prospectively recruited in a cross-sectional study. All participants underwent a Dixon-based WBMRI scan after being clinically assessed. Based on clinical findings, the CYP with JIA were divided into the active (≥1 active joint or sacroiliitis) and inactive group (no active joints or sacroiliitis). Three musculoskeletal radiologists blindly and independently reviewed the post-contrast images for joint inflammation, and this was considered present if detected by ≥2 radiologists. Peripheral joint inflammation was defined as above-normal intensity synovial enhancement with ≥1 additional feature (synovial hypertrophy, subarticular osteitis, joint effusion or periarticular soft tissue oedema). The frequency of subclinical joint inflammation (WBMRI-detected inflammation in ≥1 clinically inactive joint per participant) was compared between the control and JIA groups, and between the JIA subgroups using unpaired proportions.Results47 CYP with JIA and 13 controls were included. The median age of participants was 17 years (IQR 16 to 20) with 62% and 85% female in JIA and controls respectively. Twenty-seven (57%) participants with JIA were treated with biologic disease-modifying anti-rheumatic drugs (DMARDs) and 29 (62%) with conventional synthetic DMARDs.The frequency of WBMRI-detected joint inflammation was higher in active than inactive JIA patients (Table 1). A higher percentage of patients with JIA were detected to have subclinical inflammation by WBMRI (49%, 23/47) compared to controls (15%, 2/13), difference of 34% (95% CI: 9, 58)). One joint with inflammation was detected by WBMRI in both controls, respectively. Fifty-six per cent (14/25) of JIA patients labelled active clinically had WBMRI-detected subclinical inflammation, compared to 41% (9/22) of clinically inactive JIA patients [difference: 15% (95% CI:-13, 43)].The proportions of patients classified as active or inactive by both clinical and WBMRI assessment varied between JIA subtypes (Figure 1).ConclusionThis study demonstrated that WBMRI-detected subclinical joint inflammation is a common finding in JIA, but rare in controls. Inflammation is more common in patients with clinically active compared with inactive disease. This suggests that inflammation seen on WBMRI is a reflection of disease and not artefactual.Table 1.Frequency of WBMRI-detected joint inflammation [n (%)] compared to clinical assessmentActive JIAInactive JIADifference (95% CI)WBMRI+19 (76%)9 (41%)35% (9%,62%)-6 (24%)13 (59%)Total2522WBMRI +: participants with inflammation in ≥1 joint by WBMRI, WBMRI -: participants without joint inflammation on WBMRI. CI: confidence interval.AcknowledgementsThis work was funded by grants from the Action Medical Research and Humanimal Trust and The Albert Gubay Foundation; and by the British Society of Rheumatology. This work was supported by the Centre for Adolescent Rheumatology Versus Arthritis and the National Institute for Health Research (NIHR) University College London Hospitals (UCLH) Biomedical Research Centre (BRC).Disclosure of InterestsNone Declared.