POS1387 ENTHESEAL DOPPLER SIGNALS IN MUSCULOSKELETAL ULTRASOUND ARE INFLUENCED BY VASODILATOR DRUGS AND AGE BUT NOT BY DISEASE ACTIVITY IN PATIENTS WITH RADIOGRAPHIC AXIAL SPONDYLOARTHRITIS
Authors: M. Hallström, A. Deminger, C. Feldthusen, E. Hulander, E. Klingberg, H. Forsblad-D’elia
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Clinical assessment of enthesitis in radiographic axial spondyloarthritis (r-axSpA) is challenging and the use of musculoskeletal (MSK) ultrasound (US) is therefore increasing. Doppler signals in the presence of hypoechoic and thickened enthesis indicate active enthesitis according to the definition stated by the Outcome Measures in Rheumatology (OMERACT) US working group [1]. The significance of isolated Doppler signals at the entheses in established r-axSpA, detected by modern US equipment, is incompletely investigated. <h3>Objectives:</h3> To improve the understanding of isolated Doppler signals in US, indicative of active enthesitis in r-axSpA patients, we aimed to explore its relation to clinical signs of enthesitis. Furthermore, we sought to investigate which demographic and disease-related factors influence entheseal Doppler scores. <h3>Methods:</h3> Patients fulfilling the modified New York criteria for ankylosing spondylitis (AS) were included in the Long-term Outcome AS study (LOAS). Peripheral entheses in upper and lower extremities were examined and scored using 18MHz US, color Doppler and Smooth Microvascular Imaging (SMI), followed by clinical assessment using Leeds enthesitis index (LEI), Maastricht AS Enthesitis Score (MASES) and Spondyloarthritis Research Consortium of Canada (SPARCC) Enthesitis Index. Presence of persistent focal pain was reported on a pain mannequin, and AS Disease Activity Score (ASDAS) was registered. Blood was drawn to assess inflammatory biomarkers, and medical history including medication was acquired. Multivariable linear regression analysis was used to investigate factors associated with entheseal Doppler scores. Independent variables were chosen based on hypothetical reasoning. <h3>Results:</h3> A total of 1692 peripheral entheses in 141 patients, age (mean ± SD) 59.7 ± 11.8 years, symptom duration 34.3 ± 12.1 years, males 57%, and Human Leukocyte Antigen (HLA) B27 pos 86 % were included. US detected active enthesitis according to the OMERACT definition was overall rare, seen in 5.7 % of patients. However, Doppler signals at the entheses were common (Figure 1). Most of these findings were asymptomatic and equally distributed in males and females. A weak correlation was seen between Doppler scores and SPARCC (r = 0.29, p = 0.001), while no correlation was found between Doppler scores and other clinical enthesitis indices, nor with inflammatory biomarkers. Multivariable linear regression models (Table 1) did not detect associations between Doppler scores and BMI, sex, reported level of physical activity, occupational physical workload, ASDAS, non-steroid anti-inflammatory drugs or biologic disease-modifying antirheumatic drugs. Whereas vasodilator drugs and age both significantly influenced entheseal Doppler signals. <h3>Conclusion:</h3> Isolated Doppler signals at the peripheral entheses in established r-axSpA patients are frequently found and often asymptomatic. Doppler findings are influenced by vasodilator drugs and age but not by disease activity. Hence, US lesions indicative of active inflammation at the entheses in patients without clinically suspected enthesitis must be interpreted cautiously. Furthermore, Doppler signals are amplified by common vasodilator drugs, which need to be considered by clinicians and MSK researchers when assessing tendons. <h3>REFERENCES:</h3> [1] Bruyn GA, Iagnocco A, Naredo E, Balint PV, Gutierrez M, Hammer HB, Collado P, Filippou G, Schmidt WA, Jousse-Joulin S <i>et al</i>: <b>OMERACT Definitions for Ultrasonographic Pathologies and Elementary Lesions of Rheumatic Disorders 15 Years On</b>. <i>J Rheumatol</i> 2019, <b>46</b>(10):1388-1393. <h3>Acknowledgements:</h3> We wish to thank all the patients who chose to participate in the study. <h3>Disclosure of Interests:</h3> <b>None declared.</b>