The use of MR-imaging is recommended for the early detection of RA. Next to the small joints of the hands, foot-joints are often involved. Therefore, imaging inflammation of the feet in addition to hands may be informative, but prolongs scan-time and leads to additional costs. We studied the value of MRI of the feet alone and complementary to MRI of the hands in patients with clinically suspect arthralgia (CSA).
357 consecutively included CSA patients underwent contrast-enhanced 1.5 T-MRI of hand (MCP2-5 and wrist) and foot (MTP1-5) joints at baseline. Scans were scored for synovitis, osteitis and tenosynovitis. After ⩾1 year follow-up, the development of clinically apparent inflammatory arthritis (IA) was studied. Cox regression was performed and test characteristics were evaluated. Sensitivity analyses were performed for the outcome RA-development (2010-criteria).
MRI-detected tenosynovitis of the feet was associated with IA-development, independently from synovitis and osteitis hazard ratio (HR) (95%CI) 4.75 (2.38; 9.49), and independently from ACPA and CRP, HR 3.13 (1.48; 6.64). From all CSA patients, 11% had inflammation in hands and feet, 29% only in hands and 3% only in feet. In line with this finding, the addition of MRI-feet to MRI-hands did not increase the predictive accuracy; the sensitivity remained 77%, while the specificity decreased from 66% to 62%. Sensitivity analyses with RA development as outcome showed similar results.
Tenosynovitis at the forefeet in CSA predicted IA and RA development. Addition of foot MRI to hand MRI did not increase the accuracy. Foot MRI can be omitted to reduce scan time and costs and increase the feasibility.