LAUSR

Anti-CCP positive individuals with musculoskeletal (MSK) symptoms and subclinical synovitis on ultrasound (US) are at high risk of developing inflammatory arthritis (IA). Treatment initiation in these individuals is not accepted practice as they do not have clinical synovitis. We aimed to determine whether imaging characteristics change when individuals with pre-RA progress to IA in order to inform the optimal window of opportunity for therapeutic interventions. Anti-CCP+ at-risk individuals with MSK symptoms from the Leeds CCP cohort were selected for having US subclinical synovitis [Grey scale (GS)≥1 and Power Doppler (PD)≥1] prior to IA development and an US scan performed at clinical synovitis onset. The US protocol included the metacarpophalangeal joints (MCPJs), proximal interphalangeal joints (PIPJs), wrists, elbows, knees, second-fifth metatarsophalangeal joints (MTPJs), extensor carpi ulnaris (ECU) and finger flexor tendons (FFTs). US PD and GS synovitis were scored semi-quantitatively (0-3) according to EULAR/OMERACT. At patient level, total GS and PD scores were compared between scans. Change on US in the joints that became clinically swollen was also assessed. Wilcoxon signed-rank tests were conducted for comparisons. Forty-six CCP2+ at-risk individuals were identified (Table). The median US scan interval was 3.5 months (IQR 1.25-8.75). At patient level the overall burden of PD in the joints increased at IA progression, trending towards significance [3 (IQR 1.25-5) vs 4 (IQR 2-7.25) p = 0.063]. Overall burden of GS did not increase. There was an increase in PD in the MCPJs [0 (IQR 0-2) vs 1.5 (IQR0-3) p = 0.008] and MCP and wrist joints combined [1 (IQR 0.25-3) vs 2 (IQR 1.25-4.75) p = 0.002]. GS at the elbows also significantly increased. At joint level PD [1 (IQR(0-2) vs 2 (IQR 0-3) p = 0.036] increased in joints swollen at progression and GS increased with a trend towards significance. Non-swollen joints did not change. A marked increase in US joint inflammation is seen when CCP+ at-risk individuals with subclinical synovitis on US progress from pre-RA to clinical arthritis. This is particularly evident in the MCPJs, wrist joints and joints that become clinically swollen. Intervening when at-risk individuals have subclinical synovitis may represent a window of opportunity to prevent the rapid increase in joint inflammation which accompanies the onset of joint swelling. Disclosure K. Harnden: None. A. Di Matteo: None. D. Esperança Almeida: None. E. De Lorenzis: None. L. Duquenne: None. L. Garcia-Montoya: None. J. Nam: None. P. Emery: None. K. Mankia: None.