Treat-to-target strategy, aiming at clinical remission, has greatly improved the prognosis of RA. However, ultrasonographic subclinical synovitis is correlated with bone erosion and disease flare. The aim of this study was to evaluate whether deeper clinical remission (DAS28(ESR)≤1.98) reflects the better control of subclinical synovitis.
One hundred and twenty-six RA patients in clinical remission were enrolled in the study. Disease activity and ultrasongraphy were evaluated at baseline, and every 3 months during a 12-month follow-up. The power Doppler (PD) synovitis and synovial hypertrophy (SH) of 22 joints were recorded semi-quantitatively. The relationship between the extent of clinical remission, flare and ultrasonographic features was analysed.
In 126 RA patients, 76 achieved deep clinical remission (defined as DAS28(ESR)≤1.98) and 50 achieved mild clinical remission (defined as 1.98<DAS28(ESR)≤2.6). At baseline, PD synovitis and SH were detectable in 25 (32.9%) and 34 (44.7%) in 76 patients in deep clinical remission, which were significantly less compare with those in the mild group (32.9% vs. 72.0% and 44.7% vs. 78.0%, p<0.01 for both). In all, 54 (42.9%) patients relapsed at average of 6.8±3.3 months during follow-up. Patients in deep remission possessed not only lower risk to relapse (30.3% vs. 62.0%, p<0.01), but also longer duration of remission before relapse (8.1±3.3 vs. 5.9±3.1 months, p<0.05). Besides, applying DAS28(ESR)<1.895 to predict ultrasonographic remission defined as negativity of both PD and SH was highly accurate (p<0.001). Subclinical PD synovitis at baseline was an independent risk factor for predicting relapse in RA patients achieved clinical remission (OR 8.8 [95% CI 2.7-28.4]).
Subclinical synovitis was common in RA patients even in deep clinical remission. The deeper the clinical remission, the milder the subclinical synovitis, and the lower risk to relapse. Therefore, achieving deeper clinical remission, which reflected better control of subclinical synovitis and less tendency to flare, could be an optimised treatment target of RA.