ABS0987 ULTRASOUND FEATURES OF ENTHESITIS IN RADIOGRAPHIC AND NON-RADIOGRAPHIC AXIAL SPONDYLARTHRITIS: INSIGHTS FROM AN EGYPTION COHORT

Background: Enthesitis is a hallmark of axial spondylarthritis (axSpA), with significant diagnostic, prognostic, and treatment implications. Recent studies indicate that radiographic (r-axSpA) and non-radiographic axSpA (nr-axSpA) exist along a continuum, reflecting the same disease. Objectives: To compare clinical and ultrasound features of enthesitis in an Egyptian cohort of patients with r-axSpA and nr-axSpA, focusing on prevalence, ultrasonographic characteristics, and the impact on disease burden. Methods: This observational cohort study involved forty axSpA patients divided into two groups: twenty r-axSpA and twenty nr-axSpA according to the ASAS criteria [1]. Disease activity was assessed using ASDAS-CRP and BASDAI. Enthesitis was assessed clinically using the Spondylarthritis Research Consortium of Canada Enthesitis Index (SPARCC). Six enthesis sites were bilaterally scanned in each patient using the Esaote MyLab X5 machine with a high-frequency (6-19 MHz) linear probe. US elementary lesions of enthesitis based on the latest OMERACT definition [2] were assessed using the Belgrade UltraSound Enthesitis Score (BUSES) [3]. Results: The study included 40 axSpA patients subdivided into 20 r-axSpA and 20 nr-axSpA. Both groups were age and sex matched. There were no statistically significant differences between the two groups regarding inflammatory markers (ESR and CRP), HLA B27 and activity scores (ASDAS-CRP, BASDAI) (Table 1). Regarding the clinical assessment of enthesitis, there was no significant difference in the SPARCC index between both groups. Using US, Achilles tendon was the most frequently involved site (30 cases)with no statistical difference between both groups. Followed by plantar fascia and common extensor tendon enthesis, then the proximal patellar tendon. The least sites to be involved were the distal patellar and quadriceps tendons (in 6 cases each). In addition, there was no significant difference between r-axSpA and nr-axSpA in the BUSES scores of enthesitis. According to BUSES, six enthesis sites were bilaterally scanned in every patient. Thus, in each group, we obtained 40 scans for each enthesis site. At every enthesis, US elementary lesions of enthesitis based on the latest OMERACT definition were assessed. These included hypoechogenicity, increased enthesis thickness, doppler signals, erosions, and enthesophytes (Table 2 ). There was no significant difference in the US enthesis features at each enthesis site between the two groups. Conclusion: This study highlights the distinct features of enthesitis in Egyptian patients with r-axSpA versus nr-axSpA. The absence of statistical difference between the two groups regarding SPARCC index and BUSES scores indicates a similar burden of enthesitis. This is also confirmed by the absence of significant differences regarding each of the US elementary features of enthesitis at each entheses site. REFERENCES: [1] Akkoc N, Khan MA. ASAS classification criteria for axial spondylarthritis: time to modify. Clinical rheumatology. 2016 Jun; 35:1415-23. [2] Balint PV, Terslev L, Aegerter P, Bruyn GA, Chary-Valckenaere I, Gandjbakhch F, Iagnocco A, Jousse-Joulin S, Möller I, Naredo E, Schmidt WA. Reliability of a consensus-based ultrasound definition and scoring for enthesitis in spondyloarthritis and psoriatic arthritis: an OMERACT US initiative. Annals of rheumatic diseases. 2018 Dec 1;77(12):1730-5. [3] Milutinovic S, Radunovic G, Veljkovic K, Zlatanovic M, Damjanov N. Construct validity and sensitivity to change of Belgrade Ultrasound Enthesitis Score in patients with spondylarthritis: a pilot study. Rheumatology international. 2018 Mar;38(3):383-91. Table 1Clinical and US characteristics in Radiographic and Non-radiographic axSpATotal(n = 40)Radiographic(n = 20)Non- radiographic(n = 20)Test of sig.pSexMale24 (60%)10 (50%)14 (70%)χ 2 =1.6670.197Female16 (40%)10 (50%)6 (30%)Age (years)36.40 ± 10.7137.90 ± 8.6034.90 ± 12.52t=0.8830.383HLA.27Positive19 (47.5%)10 (50%)9 (45%)χ 2 =0.1000.752Negative21 (52.5%)10 (50%)11 (55%)ESR (up to 20 mm/hr)Median (IQR)30.60 ± 17.8830.0 ± 16.2031.20 ± 19.82t=0.2100.835CPR (up to 6 mg/dl)Median (IQR)7.25 (3.5 – 13.1)5.90 (3.85 – 9.2)10.45 (3.25 – 17.5)U= 154.00.213ASDAS-CRPMedian (IQR)3.54 ± 0.873.32 ± 0.833.76 ± 0.88t=1.6560.106BASDAIMedian (IQR)5.98 ± 1.785.81 ± 1.706.16 ± 1.89t=0.6240.536SPARCC indexMedian (IQR)1.50 (0 - 4)1.50 (0 – 3.5)1.50 (0 – 1.0)U= 199.00.977Belgrade scoreMedian (IQR)2.50 (1 – 6.50)2.0 (0.50 – 3.0)4.50 (1.5 – 9.0)U=131.500.061Achilles tendon30 (75%)14 (70%)16 (80%)χ 2 =0.5330.465Plantar fascia9 (22.5%)2 (10%)7 (35%)χ 2 =3.584 FE p=0.127Distal PT6 (15%)2 (10%)4 (20%)χ 2 =0.784 FE p=0.661Proximal PT8 (20%)2 (10%)6 (30%)χ 2 =2.500 FE p=0.235Quadriceps T6 (15%)3 (15%)3 (15%)χ 2 =0.000 FE p=1.000CET9 (22.5%)2 (10%)7 (35%)χ 2 =3.584 FE p=0.127PT: Patellar tendon T: Tendon CET: Common extensor tendonIQR: Inter quartile range, SD: Standard deviationχ 2 : Chi square test t: Student t-test U: Mann Whitney test FE: Fisher Exact testP: ≤ 0.01 is considered significant Table 2Ultrasound elementary lesions of enthesis in Radiographic and Non-radiographic axSpARadiographic (n=20 patients)Non- radiographic (n=20 patients)ATPFDPTPPTQTCETATPFDPTPPTQTCETHypoechogenicityN(40)434321442123%10.07.510.07.55.02.510.010.05.02.55.07.5IncreasedthicknessN(40)634111871011%15.07.510.02.52.52.520.017.52.50.02.52.5Doppler signalN(40)002002100000%0.00.05.00.00.05.02.50.00.00.00.00.0ErosionN(40)000000100001%0000002.50.00.00.00.00.0EnthesophyteN(40)19122232602659%47.52.55.05.05.07.565.00.05.015.012.522.5AT: Achillies tendon PF: Plantar fascia DPT: Distal patellar tendon PPT: Proximal patellar tendon QT: Quadriceps tendon CET: Common extensor tendon Acknowledgements: NIL . Disclosure of Interests: None declared . © The Authors 2025. This abstract is an open access article published in Annals of Rheumatic Diseases under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Neither EULAR nor the publisher make any representation as to the accuracy of the content. The authors are solely responsible for the content in their abstract including accuracy of the facts, statements, results, conclusion, citing resources etc.

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