Diagnostic efficacy of ultrasound detection of enthesitis in peripheral spondyloarthritis.

Objective: We investigated the diagnostic efficacy of power Doppler ultrasound (PDUS) to detect enthesitis in Japanese patients with peripheral spondyloarthritis (SpA). Methods: This was a single-center cohort study of patients with peripheral symptoms suggestive of SpA. Articular synovia, tendons, and entheses were assessed by PDUS at baseline. Clinical, laboratory, and radiologic findings and classification criteria for SpA were also evaluated. Results: 136 patients were consecutively evaluated. A definite diagnosis was obtained in 111 patients, including 72 with SpA and 39 non-SpA. Among the patients with SpA, PDUS demonstrated articular synovitis in 40 of the 72 patients (56%), tenosynovitis or peritendinitis in 48 (67%), and enthesitis in 63 (88%). Considering PDUS alone, enthesitis in at least one site was the most useful means of differentiating SpA from non-SpA (sensitivity 87.5%; specificity 82.1%; accuracy 85.6%; positive likelihood ratio 4.88). Combining that finding along with fulfillment of Amor, European Spondyloarthropathy Study Group, or Assessment of SpondyloArthritis international Society criteria for peripheral SpA increased the specificity of the diagnosis (92.5%, 92.3%, and 97.4%, respectively). Conclusion: PDUS enthesitis is useful for the diagnosis of SpA with peripheral symptoms. Combining PDUS enthesitis with established SpA classification criteria is beneficial in diagnosing peripheral SpA.