AB1279 UTILITY OF A DIAGNOSTIC ALGORITHM IN THE ASSESSMENT OF LARGE VESSEL VASCULITIS
Authors: H. F. Avalos Bogado, G. A. Añez Sturchio, E. Trallero Araguas, E. Espartal López, S. Sandoval Moreno, A. D. Ulloa Navas, J. J. De Agustin
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Giant cell arteritis (GCA) is the most prevalent type of primary systemic vasculitis among individuals aged 50 and above. Imaging techniques such as ultrasound (US), magnetic resonance imaging (MRI), and {18F}-fluorodeoxyglucose positron emission tomography (PET-CT) have emerged as crucial diagnostic tools due to their non-invasive nature, higher sensitivity and availability compared to temporal artery biopsy (TAB). <h3>Objectives:</h3> To evaluate the effectiveness of an algorithm based on imaging techniques in the diagnosis of GCA. Additionally, to assess the potential reduction in costs and unnecessary investigations during the diagnostic process. <h3>Methods:</h3> The project consists of two phases. The first phase involved a retrospective analysis of a cohort suspected of having GCA, derived from outpatient consultations (OC) and hospitalizations in a tertiary hospital's Rheumatology department (February 2021-December 2022). A diagnostic evaluation was conducted using clinical criteria and imaging techniques (US, PET-CT, TAB). US examinations were performed according to a standardized protocol within the Rheumatology service. In the second phase, the proposed diagnostic algorithm (Figure 1) was retrospectively applied, and the results were compared with the pre-algorithm phase. All patients provided their consent for participation. <h3>Results:</h3> The study included 40 patients (80% women, n=32; 20% men, n=8), with a mean age of 72.55. All patients had clinical suspicion and 100% underwent US examinations with findings suggestive of GCA in 10 individuals (25%). TAB was performed in 9 patients (22.5%) and 3 of them (7.5%) had compatible results. PET-CT was conducted in 30 (75%) with conclusive results observed in 13 cases (32.5%). A final diagnosis of GCA was established in 16 patients (40%): clinical criteria + US in 1 patient (6.25%); clinical criteria + US + PET-CT in 8 (50%); clinical criteria + US + PET-CT + TAB in 7 (43.75%) (Table 1). Notably, among the 6 patients admitted to the hospital, 5 presented with initial clinical manifestations of anterior ischemic optic neuritis (AION). Within the diagnosed group, 10 individuals received corticosteroid treatment for at least 5 days prior to undergoing imaging techniques. Retrospective application of the algorithm to 8 patients (20%) with compatible US findings indicated that no further investigations would have been necessary (TAB + PET-CT in 5 patients and PET-CT alone in 3). Consequently, a total of 13 unnecessary supplementary tests could have been avoided. The maximum cost per patient amounted to €1117 (PET-CT €997, US €70, TAB €50). Implementation of the algorithm could have resulted in cost savings of €8176 and reduced iatrogenesis in this subgroup. <h3>Conclusion:</h3> The utilization of an algorithm represents a practical and applicable tool in the diagnostic process of GCA. US serves as a valuable screening method in the initial evaluation, effectively reducing costs and redundant investigations in patients with compatible results and a high clinical suspicion. In cases where both clinical criteria and US findings are negative, it aids in excluding GCA as a diagnosis. <h3>REFERENCES:</h3> <b>NIL.</b> <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> <b>None declared.</b>