POS0087 QUANTITATIVE VASCULAR US AND THE OMERACT GCA US SCORE HAS ADDITIONAL DIAGNOSTIC AND PROGNOSTIC VALUE IN GCA
Authors: C. Kirby, R. Flood, S. Cowley, E. Finlay, R. Mullan, G. Murphy, D. Kane
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Ultrasound (US) is a well-validated tool for diagnosing Giant Cell Arteritis (GCA) [1]. Little is known about its role in prognostication or disease-monitoring. Different quantification scores have been proposed for vascular US in GCA including the recent OMERACT GCA US (OGUS) score [2]. <h3>Objectives:</h3> This study evaluates the Halo Count, Halo Score and OGUS score in a prospective cohort of GCA patients and assesses the role of sonographic vasculitis quantification in the diagnosis and management of GCA. <h3>Methods:</h3> US of superficial temporal (STA) and axillary arteries (AA) was performed at 0, 1, 3, 6 and 12 months in 57 patients with GCA (diagnosis confirmed by two rheumatologists in agreement). Mean Halo Counts (HC), Halo Scores (HS) and OGUS were calculated at each study timepoint; Wald tests were used to determine the significance of longitudinal trends. Time-to-normalization of HC, HS and OGUS were evaluated with abnormal thresholds considered ≥1, ≥21 and ≥1.0 respectively. Correlation coefficients were compared between all clinical and biochemical parameters and baseline US outcome scores (HC, HS and OGUS) to determine which patient factors may predict US outcomes. Correlation coefficients were calculated and AUC analysis was performed for all clinical, biochemical and US parameters to determine reliability for predicting future adverse events (GCA diagnosis, GCA flare, ischaemic complications and future biologic requirement). DeLong test was used to validate the OGUS score. AUC analysis was performed to determine the optimal cut-off IMT in each branch of STA and AA for GCA diagnosis. <h3>Results:</h3> 48/50 patients were followed up at 6 months and 27 at 12 months. Mean HC, HS and OGUS all declined over 12 months with statistically significant differences between each study timepoint (Figure 1). Of 48 patients, HC, HS and OGUS normalized in 21, 32 and 39 patients respectively by 6 months and no association was seen between time-to-normalisation and adverse events. Fulfilling 2022 ACR/EULAR Classification Criteria showed moderate correlation with baseline HC, HS and OGUS with higher classification criteria scores showing strong correlation with higher US outcome scores (Table 1). HC, HS and OGUS were superior to all clinical and laboratory parameters for predicting future adverse events with OGUS outperforming HC and HS (Table 1). Incidence of ischaemic events were too low to determine significance. The optimal IMT cut-offs for diagnosing GCA in our cohort were: Common STA 0.42mm, Frontal STA, 0.35, Parietal STA 0.29, Axillary Artery 0.75 with no significant difference observed between groups with and without cardiovascular risk factors (Table 1). <h3>Conclusion:</h3> Quantifying degrees of inflammation on vascular US has both diagnostic and prognostic value in GCA as does serial scoring during follow-up. Higher baseline US outcome scores were associated with a higher likelihood of GCA diagnosis, flaring within 12 months and requirement for future biologic therapy. OGUS correlated with other US quantification scores but normalized earlier and performed better in predicting adverse events. <h3>REFERENCES:</h3> [1] Luqmani R et al. TABUL: a diagnostic accuracy and cost-effectiveness study. Health Technol Assess. 2016;20(90):1-238. [2] Nielsen BD et al. Ultrasonography in the assessment of disease activity in cranial and large-vessel giant cell arteritis. Rheumatology (Oxford, England). 2023;62(9):3084-94. <b>Table 1.</b> <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> <b>None declared.</b>