Objective  To analyze the incidence, clinical characteristics and influencing factors of subclinical synovitis in patients with rheumatoid arthritis (RA).

  Methods  The occurrence of subclinical synovitis in 146 RA patients with clinical remission after 6 months of treatment was analyzed. According to the results of musculoskeletal ultrasound, they were divided into subclinical synovitis group and ultrasound remission group, and clinical and ultrasonic features of two groups were compared. The predictive factors of subclinical synovitis in RA were evaluated by receiver operating characteristic (ROC) curve. Effect of anti-rheumatism treatment on the incidence of subclinical synovitis in RA patients was observed.

  Results  At 6 months of treatment in RA patients who met the remission criteria of Disease Activity Score in 28 joints calculated by erythrocyte sedimentation rate (DAS28-ESR), Disease Activity Score in 28 joints calculated by C reaction protein (DAS28-CRP), Clinical Disease Activity Index (CDAI) and Simplified Disease Activity Index (SDAI), the subclinical synovitis was found in 49 cases (45.4%), 66 cases (46.2%), 35 cases (41.7%) and 34 cases (41.0%) respectively. The CRP level and DAS28-ESR, DAS28-CRP, CDAI and SDAI scores in the subclinical synovitis group were significantly higher than those in ultrasound remission group (P=0.020, 0.007, 0.001, 0.002 and 0.001). The synovial hyperplasia score (GS score) in subclinical synovitis group was significantly higher than that in ultrasound remission group (P=0.001). ROC curve showed that GS score and synovial blood flow score at baseline could predict the occurrence of subclinical synovitis. The incidence of subclinical synovitis in RA patients decreased after 6 months and 1 year of treatment.

  Conclusion  Patients with RA may still have subclinical synovitis after reaching clinical remission criteria, while patients with subclinical synovitis have higher CRP level, disease activity and GS scores. GS score and synovial blood flow score at baseline can predict the occurrence of subclinical synovitis. Effective anti-rheumatic therapy can reduce the incidence of subclinical synovitis.