Imaging Modality Agreement in Finger Lesions of PsA Patients

About 30% of psoriasis patients suffer from psoriatic arthritis (PsA). The inflammatory disease can unfold with inflammatory and structural changes including synovitis, tenosynovitis, and erosions. While ultrasound and magnetic resonance imaging (MRI) are both highly regarded imaging modalities for peripheral arthritis assessment, discrepancies between the two in assessments of PsA patients is unclear. This study, presented at the American College of Rheumatology/Empowering Rheumatology Professionals Annual Meeting, analyzed the agreement between ultrasound and MRI in detecting finger lesions in PsA patients, as well as the sensitivity and specificity of ultrasound with MRI as gold standard.

PsA patients were assessed by ultrasound and MRI for the metacarpophalangeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints of one matched hand. Image assessors were blinded to the clinical data, and ultrasound and MRI were performed no more than three days apart. Nonsteroidal anti-inflammatory drug (NSAID) use was paused for three days prior to evaluation.

The study population included 60 PsA patients (mean age, 52 years; female-to-male ratio was 6:4); 300 MCP, 300 PIP, and 240 DIP were assessed by ultrasound and MRI. Ultrasound and MRI yielded similar rates of synovitis, flexor tenosynovitis, and erosions. The MCP joints had a higher prevalence of synovitis (19.3% for ultrasound and 13.7% for MRI) and flexor tenosynovitis (5.7% for ultrasound and 6.3% for MRI) than the PIP and DIP joints. The researchers reported ultrasound-MRI absolute agreement and kappa values of 84%–95% with moderate to substantial kappa values (0.411–0.654), 94%–97% with fair to moderate kappa values for tenosynovitis (0.208–0.468) and 98% with fair to moderate kappa values for erosions (0.211–0.492). Ultrasound sensitivity and specificity with MRI for synovitis ranged from 0.5–0.78 and 0.87–0.97 based on the specific joint, and for flexor tenosynovitis 0.25–0.47 and 0.97, respectively.

The researchers concluded here that ultrasound and MRI presented “moderate to good agreement” in detecting inflammatory and destructive changes, while “the sensitivity is better for synovitis compared to flexor [tenosynovitis].”