Pos0928 Assessing Metrics of Real World Gca Ultrasonography Against the Halo Count, Halo Score and Ogus

Background: The 2022 EULAR guidelines state "Ultrasound of temporal and axillary arteries should be considered as the first imaging modality to investigate mural inflammatory changes in patients with suspected GCA", assuming appropriately trained experts and quality equipment is available 1. This caveat recognised the highly technical nature of GCA ultrasound (US), and anecdotally scepticism remains about the use of US as a diagnostic tool in clinical practice. Objectives: We aimed to assess the quality of US in clinical practice against 3 recently published scoring systems developed to aid diagnosis and monitoring respectively (Halo Score, Halo count, OGUS) 2,3. Methods: Patients seen in the Royal Perth Hospital GCA FTC clinic since Dec 2019 to July 2023 with stored US images were included in this audit. Patient notes, letters, and blood test results were reviewed to collect demographic and diagnostic information. Ultrasonography was supervised by 1 of 2 consultant rheumatologists with GCA US training. The US was performed on a GE Logic e with a 6-12 MHz probe and a 18 MHz probe with settings optimised according to EULAR guidelines 4. The bilateral common superficial temporal arteries, frontal, parietal and axillary vessels were assessed for stenosis/occlusion, halo, and compressibility. This allowed the Halo Count to be determined retrospectively. The Ultrasonographer-clinician also assigned a value of "positive, inconclusive or negative" to the scan at the time of imaging. In this analysis, an inconclusive label was assigned a negative label. The stored US images were retrospectively measured, by a single reader, to allow calculation of the Halo Score (using those segments designated to have a halo at the time of imaging) and the OGUS. The Clinician's opinion of a positive US as assessed at the time of the visit, was compared against the Halo Score (HS), Halo count (HC) and the OMERACT GCA US Score (OGUS), to determine the quality of the US undertaken in our FTC. We calculated sensitivity (Sn), specificity (Sp), positive predictive value (PPV) and negative predictive value (NPV) of the HS, HC, OGUS and sonographers opinion against the clinical diagnosis at 6 months (Dx at 6 months) and Temporal Artery Biopsy (TAB) positivity. Results: Demographics, Dx at 6 months, TAB and US results are presented in Table 1. 164 people presenting to the clinic had an ultrasound of their temporal arteries with stored images, and were followed up long enough for a diagnosis at 6 months. Sensitivity, Specificity, PPN and NPV of the US systems are presented in Graph 1. 57 people presenting to the clinic had an ultrasound of the temporal arteries with stored images and had a TAB at baseline. Sn, Sp, PPV and NPV of the US systems are presented in Graph 1. Conclusion: In our real world experience, the opinion of the sonographer (dichotomised) at the time of presentation had very good Sn, Sp, PPV and NPV, and performed well against retrospectively applied HS, HC and the OGUS, recognising the OGUS is not a diagnostic tool. REFERENCES: 1 Christian Dejaco, Sofia Ramiro, Milena Bond, et al. EULAR recommendations for the use of imaging in large vessel vasculitis in clinical practice: 2023 update. Annals of the Rheumatic Diseases Published Online First: 07 August 2023. doi: 10.1136/ard-2023-224543. 2 Dejaco C, Ponte C, Monti S, et al. The provisional OMERACT ultrasonography score for giant cell arteritis. Ann Rheum Dis. 2023 Apr;82(4):556-564. doi: 10.1136/ard-2022-223367. Epub 2022 Dec 12. PMID: 36600183. 3 van der Geest KSM, Borg F, Kayani A, et al. Novel ultrasonographic Halo Score for giant cell arteritis: assessment of diagnostic accuracy and association with ocular ischaemia. Annals of the Rheumatic Diseases 2020;79:393-399. 4 Dejaco C, Ramiro S, Bond M, et al EULAR recommendations for the use of imaging in large vessel vasculitis in clinical practice: 2023 update. Annals of the Rheumatic Diseases Published Online First: 07 August 2023. doi: 10.1136/ard-2023-224543. Acknowledgements: The clinic was established with a Fellowship from the Health Department of WA. Disclosure of Interests: Helen Keen Not in the last 3 years, Not in the last 3 years, Not in the last 3 years, Not in the last 3 years, Neve Keen: None declared, Julia Murdoch: None declared, Andrew Taylor: None declared, Kylan Pathmanathan: None declared, Charlotte Woollard: None declared, Kimberly Loh: None declared, Jean-louis Desousa: None declared.