Persistence of subclinical sonographic joint activity in rheumatoid arthritis in sustained clinical remission

Background Sonographic assessment, measuring grey scale (GS) and power Doppler (PD) signals, is a sensitive tool for the evaluation of inflammatory joint activity in patients with rheumatoid arthritis (RA). We evaluated the persistence of PD and GS signals in previously clinically active RA joints that have reached a state of continuous clinical inactivity. Methods We performed sonographic imaging of 22 joints of the hands of patients with RA, selected all joints without clinical activity but showing ongoing sonographic signs of inflammation, and evaluated the time from last clinical joint activity. Results A total of 90 patients with RA with 1980 assessed joints were included in this study. When comparing the mean time from clinical swelling, we found a significantly longer period of clinical inactivity in joints showing low sonographic activity (mean SD time from swelling of 4.1 +/- 3.2 vs 3.1 +/- 2.9 years for PD1 vs PD >= 2, p=0.031 and 4.5 +/- 3.4 vs 3.3 +/- 3.2 years for GS1 vs GS >= 2, p <= 0.0001). Conclusions We conclude that subclinical joint activity is long-lasting in RA joints in clinical remission, but attenuates over time. The latter conclusion is based on the observed shorter time duration from last clinical activity for strong compared with weaker sonographic signals.