Superb microvascular imaging (SMI) for evaluating hand joint lesions in patients with rheumatoid arthritis in clinical remission

The utility of superb microvascular imaging (SMI) for evaluating hand joint lesions in patients with rheumatoid arthritis (RA) in clinical remission is unreported. This study aimed to compare SMI and power Doppler imaging (PDI) for the evaluation of hand joint lesions in these patients. Twenty-six patients with RA in clinical remission were enrolled. A total of 572 joints (52 wrist, 260 proximal interphalangeal, and 260 metacarpophalangeal joints) were detected by SMI and PDI. A semi-quantitative scale of 0-3 was used to compare the detection of synovial blood flow signal by SMI and PDI. Inter-observer agreement for the assessment of SMI and PDI scores was measured with kappa values. In the ten healthy volunteers, SMI and PDI signals were both scored 0. In the 26 RA patients, the remission rate via PDI was 65.4% but was only 42.3% via SMI. SMI also detected microvessel flow signal in seven patients diagnosed with clinical remission via PDI. Moreover, a total of 106 blood flow signals (18.5%) were detected by SMI, while 50 blood flow signals (8.7%) were detected by PDI. Compared with PDI, SMI increased 18.0% of power flow signals from Grade 0-1 and increased 13.7% of power flow signals from Grade 1-2. One joint classified as Grade 1 by PDI was classified as Grade 0 by SMI. Inter-observer agreement for PDI and SMI semi-quantitative scoring was moderate (kappa = 0.463). SMI seems more sensitive than PDI for detecting hand joint lesions in RA in clinical remission PDI, and could aid the achievement of true remission in RA patients.