AB0597 CAN A ONE-HOUR QUANTITATIVE ASSESSMENT OF FDG-PET-CT (MODIFIED-PETVAS) BE USEFUL IN TAKAYASU’S ARTERITIS?
Authors: Sema Kaymaz Tahra, Salih Özgüven, Ali Ugur Unal, Fatma Alibaz-Oner, Tunc Ones, Tanju Yusuf Erdil, Haner Direskeneli
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background:</h3> FDG-PET-CT is suggested as an imaging method for the assessment of disease activity in Takayasu's arteritis (TAK). Recently PETVAS, a quantitative score assessed at 2-hours is suggested as an imaging tool for TAK (1). However, most studies with FDG-PET-CT in the literature is performed at one-hour, similar to suggested as the minumum time in recent EULAR recommendations for the use of imaging in large-vessel vasculitis (2). <h3>Objectives:</h3> In this study, we aimed to evaluate the value of a modified <i>PET Vascular Activity Score (PETVAS)</i> (performed at one-hour) during the initial diagnosis and follow-up of TAK patients. <h3>Methods:</h3> Patients who are diagnosed with Takayasu's arteritis and underwent FDG-PET-CT imaging during their follow-up were evaluated in this study retrospectively. FDG-PET-CT imaging was performed at the first hour of FDG uptake. Demographic and clinical characteristics of the patients were recorded from patients' charts. Physician's Global Assessment (PGA) was used to determine clinical activity. In the modified PETVAS scoring system, 9 arterial areas (Ascending Aorta, Aortic Arch, Descending Thoracic Aorta, Abdominal Aorta, Right Carotid Artery, Left Carotid Artery, Innominate Artery, Right Subclavian Artery, Left Subclavian Artery) were scored between 0 and 3 according to the FDG uptake, as originally suggested. The degree of arterial involvement was scored as 0= no uptake, 1=less than liver involvement, 2=equal involvement to liver, 3=greater than liver involvement (maximum score = 27). The visual analysis using the liver FDG uptake as the reference was also assessed and compared with m-PETVAS score. <h3>Results:</h3> Thirty-eight imagings of 28 patients (F/M=22/6, mean age=39,7 ± 14,8 years) were evaluated. Median CRP level was 16,7 (2-126) mg/L. Median m-PETVAS score was 5 (0-27) and m-PETVAS was significantly higher in patients who were accepted as active according to PGA (median PETVAS score 6,0 vs 1,5, p=0.03). Similarly, patients who have an active PET assessed with only visual analysis (VA) have higher m-PETVAS scores than patients who were VA inactive (median score 9,0 vs 2,5, p= 0.000). A positive correlation was observed between the CRP levels before imaging and total m-PETVAS scores (p=0.01, rho=0.52). In 35/38 imaging assessments the score was &gt;0 and the immunosuppressive agent was changed in 24 (63%) of these patients. Twenty-seven patients received corticosteroids before imaging. No difference in PETVAS scores were present between patients who were taking steroids vs non-steroid use. In 11 patients (29%), PET involvement other than the 9 arterial areas used for assessing the score, were observed. The mean age of this group was higher than the rest of the group (47,2±14,7 vs 35,7±11,2 years). <h3>Conclusion:</h3> FDG-PET-CT assessment with a modified PETVAS (assessed at one hour) demonstrated higher scores in patients with Takayasu's arteritis who were considered clinically active or had increased CRP. However, the scores were lower compared to the original scoring performed at two hours. Therefore, whether one hour investigations have sufficient discriminatory value requires further studies. <h3>References</h3> [1] - Grayson PC, Alehashemi S, Bagheri AA, et al. 18 F-Fluorodeoxyglucose-Positron Emission Tomography As an Imaging Biomarker in a Prospective, Longitudinal Cohort of Patients With Large Vessel Vasculitis. Arthritis Rheumatol. 2018;70:439-449. [2] - Dejaco C, Ramiro S, Duftner C, et al. EULAR recommendations for the use of imaging in large vessel vasculitis in clinical practice. Ann Rheum Dis. 2018;77:636-643. <h3>Disclosure of Interests:</h3> None declared