Evaluation of remission in patients with radiographic axial spondyloarthritis using an ultrasonography-based enthesitis score: a cross-sectional study.

Introduction: This study aimed to evaluate ultrasonographic entheseal abnormalities in patients with radiographic axial spondyloarthritis (r-axSpA) who were in clinical remission for at least 6 months and receiving either nonsteroidal anti-inflammatory drugs (NSAIDs) or biologic agents. Material and methods: Seventy-two r-axSpA patients were included, divided into NSAID users (n = 23) and biologic agent users (n = 49). Demographic and clinical data were recorded. Ultrasound assessment was performed bilaterally at 10 entheseal sites using a 7-13 MHz linear probe. Elementary lesions defined by OMERACT - hypoechogenicity, thickening, power Doppler (PD) signal, calcification, enthesophyte, and bone erosion - were evaluated and scored on a scale of 0-3. Inflammation scores included hypoechogenicity, thickening, and PD signal; chronicity scores included bone erosion, enthesophyte, and calcification. Results: A total of 720 entheseal sites were analyzed. The quadriceps tendon was the most frequently affected site (98.6%), followed by the distal patellar tendon (94.4%), Achilles tendon (70.8%), and plantar fascia (70.8%). Hypoechogenicity, thickening, enthesophyte formation, and bone erosion were the most common abnormalities, while PD signals and calcifications were rare. Nonsteroidal anti-inflammatory drug users showed significantly higher C-reactive protein (CRP) (0.62 ±0.53 vs. 0.41 ±0.27 mg/dl, p = 0.027) and erythrocyte sedimentation rate (ESR) levels (11.91 ±7.72 vs. 7.65 ±5.66 mm/h, p = 0.010) than biologic users, despite similar Axial Spondyloarthritis Disease Activity Score with CRP score. Mean inflammation, tissue damage, and total ultrasound (US) enthesitis scores were 4.85 ±4.37, 6.44 ±4.44, and 11.24 ±8.21, respectively, with no significant difference between treatment groups. Seven biologic-treated, overweight, or obese patients had markedly elevated total US scores (30.43 ±5.83), suggesting persistent entheseal inflammation and structural damage. Conclusions: Ultrasound-based enthesitis scoring may reveal subclinical disease activity in r-axSpA patients in remission, highlighting the added value of integrating musculoskeletal US into disease monitoring.