Ultrasound Assessment of Entheses and Correlations Between Disease Activity and Ultrasound Scores in Ankylosing Spondylitis: A Cross Sectional Study

Abstract

Background: An increasing number of studies have applied ultrasound (US) to evaluate enthesitis in spondyloarthritis. However, there is no clear agreement on which sites should be evaluated for enthesitis. Furthermore, there are different opinions on whether US can monitor disease activity. The objectives of this study were to evaluate the common involvement of entheses and correlations between disease activity and US scores in ankylosing spondylitis (AS).Methods: A cross-sectional, monocentric, and controlled study was performed. US was used to scan 34 entheses per person and the Madrid sonography enthesitis index (MASEI) score was used. US scores were used to evaluate the elemental lesions of hypoechogenicity, thickness, erosion, calcification, bursitis, and Doppler signal. Disease activity was assessed by Disease Activity Score–C reactive protein (ASDAS-CRP) and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI).Results: 104 patients with AS and 50 control subjects were included. A total of 5236 entheses were assessed. Compared with the control subjects, only three entheses – the Achilles tendon (AT), sternoclavicular joint (SCJ), and costochondral joint (CCJ) – showed significant differences in the AS group (p < 0.05). Patients with high disease activity (ASDAS-CRP ≥ 2.1) had higher scores than patients with low activity (ASDAS-CRP < 2.1) in erosion (p = 0.02). Patients who were categorized in very high disease activity (ASDAS-CRP ≥ 3.5) had a higher score in erosion (p = 0.02). The erosion score was moderately associated with ASDAS-CRP and BASDAI (r = 0.44, r = 0.21).Conclusions: The commonly involved entheses were the AT, SCJ, and CCJ in AS. Erosion occurred more often in patients with disease activity or high activity. Erosion would be more useful for monitoring disease activity in AS.