LAUSR

Background Independent predictive value of ultrasonography-detected digit flexor tenosynovitis has been reported for rheumatoid arthritis (RA) development in patients with early arthritis, and it also was reported as an independent risk factor of flare in remission RA. However, proximal interphalangeal joints (PIPJs) were scarcely evaluated by MRI, nor recommended by RAMRIS so far. Objectives To explore the characteristics of MRI-detected inflammation in bilateral PIPJs in early RA patients and its clinical significance. Methods Early RA patients who fulfilled 2010 ACR/EULAR classification criteria with disease duration ≤1 year and DAS28-CRP≥2.6 were recruited. New methodology of 3.0T whole-body MRI with contrast-enhanced imaging was used to scan bilateral hands simultaneously. MRI tenosynovitis, synovitis and osteitis were scored referring to the 2016 updated RAMRIS. Clinical data were collected. Results 1) Among 75 patients recruited, the median age was 49 years old (IQR: 38-59) with 71% female. The median disease duration was 7 months (IQR: 3-12) and the mean DAS28-CRP was 5.1 (IQR: 4.2-6.1). Forty-four patients (59%) were treatment-naïve who had never taken any DMARDs or glucocorticoids before recruitment. Both joint tenderness and swelling were present the most frequently in PIPJ2 and PIPJ3 (48%∼61% and 43%∼56%, respectively, Figure 1A).2) MRI tenosynovitis, synovitis and osteitis were detected in 84%, 100% and 83% of the patients; and respectively in 21%∼44%, 43%∼56% and 5%∼11% of various PIPJs. There were 12%∼30%, 28%∼40%, and 2%∼8% of PIPJs without tender or swollen showing MRI tenosynovitis, synovitis and osteitis respectively. When non-dominant hands were used as self-control, the frequency of digit flexor tenosynovitis in dominant interphalangeal joint (IPJ) of thumb, PIPJ2 and PIPJ4 was 16%∼18% higher than the non-dominant counterparts, indicating a potential impact of overuse on dominant tenosynovitis. 3) Tenosynovitis affects periarticular digit flexor tendon compartment and 65%∼87% of tenosynovitis in PIPJs occurred together with synovitis in joint cavity and/or osteitis in subchondral bone. Among tender IPJ of thumb, 50% of them showed MRI synovitis together with digit flexor tenosynovitis, which was significantly more than those who showed MRI synovitis alone (21%, Chi-square test, p<0.017). Similar trend was found in tender PIPJ2 (45% vs. 26%, p<0.01). Generalized Estimating Equations with multivariate logistic regression showed not only MRI synovitis but also digit flexor tenosynovitis in bilateral PIPJs independently had more than twice probability of joint tenderness (both p<0.01, Figure 1B). Conclusion This preliminary study showed MRI-detected digit flexor tenosynovitis in bilateral PIPJs contributed to joint tenderness in early RA patients independently of synovitis which should not be ignored in clinical practice. Acknowledgement This work was supported by National Natural Science Foundation of China [grant numbers 81601427 and 81671612), Natural Science Foundation of Guangdong Province [grant numbers 2016A030313307, 2017A030313470 and 2017A030313576], State Scholarship Fund from China Scholarship Council [file number: 201806385034] and Yat-Sen Scholarship for Young Scientists [to Mo YQ] Disclosure of Interests None declared