Background The goal of rheumatoid arthritis (RA) treatment is to achieve clinical, functional, and structural remission. Tocilizumab (TCZ), an anti-interleukin-6 receptor monoclonal antibody agent, has a high compliance rate and can maintain clinical and functional remissions. Imaging examination for structural remission is advanced; however, the accuracy of evaluation results is inconsistent. Joint ultrasonography is an important measurement tool to comprehensively evaluate synovitis according to the presence or absence of blood flow signal. However, only a few reports have evaluated the efficacy of TCZ by using joint ultrasonography.

Objectives The objective of this study was to evaluate the correlation between positive blood flow signal on joint ultrasonography and progression of joint destruction in patients with RA treated with TCZ for 4 years.

Methods Among 111 patients who were treated with TCZ in the Akita Orthopedic Group on Rheumatoid Arthritis (AORA), 16 patients were receiving TCZ for 4 years or longer and enrolled this study. We examined age, sex, disease duration, C-reactive protein (CRP) level, MMP3 level, DAS28-ESR score, and clinical disease activity index (CDAI) at the start of TCZ administration and once a year. Moreover, we examined for blood flow signal (power Doppler signal) on joint ultrasonography at 4 years and modified total Sharp score (mTSS) on radiography at the baseline and once a year. Joint ultrasonography was performed in 34 joints, including bilateral proximal interphalangeal and metacarpophalangeal joints of the five fingers, wrists, knees, and metatarsophalangeal joints of the five toes in all of the patients, as well as other joints with symptoms. The subjects were divided into the P(+) and P(−) groups according to the presence or absence of blood flow signal on joint ultrasonography at 4 years. Eight patients were classified into the P(+) group and 8 were the P(−) group. Furthermore, progression of joint destruction by using mTSS were compared among both groups.

Results The mean patient age was 52 (range, 38–63) years, and the mean disease duration was 92 (range, 30–159) months. Women accounted for 69% of the patients. At the start of TCZ administration, no significant differences in age, proportion of women, disease period, CRP, CMMP3, and CDAI were observed between both groups. However, the DAS28-ESR score was significantly higher in the P(+) group than in the P(−) group (p=0.0279). Before the start of TCZ therapy, the scores of mTSS/year were 3.9 in the P(+) group and 2.7 in the P(−) group, showing no significant difference. After the start of TCZ therapy, the scores of mTSS/4 years were 3.4 in the P(+) group and 0.2 in the P(−) group, showing a significant difference (p=0.0347).

Conclusions The presence of positive blood flow signal on joint ultrasonography at 4 years was significantly correlated with progression of joint destruction in patients with RA treated with TCZ.

Acknowledgement We wish to thank the members of AORA.

Disclosure of Interest None declared