Six-joint ultrasound in rheumatoid arthritis: a feasible approach for implementing ultrasound in remission

Subclinical disease activity in rheumatoid arthritis (RA) detected by imaging methods is predictive for flares and damage. Lack of time is the major limitation for not screening for subclinical disease in routine practice. We aimed to determine the most feasible protocol to screen patients with no clinical disease activity by ultrasound (US).

A hundred consecutive RA patients with no clinical activity according to the physician had an US scan for 38 joints. The prevalence of power Doppler (PD) signal in each joint was determined and different combinations of joints were assessed for their ability to capture this information. The most practical combination with a good sensitivity was tested in another group of 50 RA patients.

Having any PD signal was not linked to the disease activity parameters whereas presence of PD of ≥2 was associated with higher DAS28CRP. Sixty patients had at least one joint with PD of grade ≥2 (60%). A combination of the wrists and 2nd-3rd MCP joints bilaterally (PD-6 joints) was able to detect 45/60 (75%) cases with PD signals and 45% of the whole patient population. The correlation between PD-38 and PD-6 joints was excellent (r=0.820, p<0.0001). PD-6 joints in the 2nd cohort was also able to detect 22/50 (44%) of the whole group.

Subclinical disease activity could be detected in 60% of RA patients when 38 joints screened by US. Limiting the screening to wrists, 2nd-3rd MCPs bilaterally was acceptable as it detected 75% of cases with subclinical disease and increased the feasibility.