Background: Takayasu arteritis (TA) is a condition characterized by major large-vessel vasculitis (LVV), and is most commonly found in young women (age <40 years) of East Asia countries. 18F-FDG-PET/CT has been widely used in the diagnosis and follow-up of cancers to gather functional information based on metabolic activity. In the present study, we evaluated the value of different parameters in 18F-FDG-PET/CT for assessing active TA disease, and we establish a simple, quantifiable, and effective disease activity evaluation model based on 18F-FDG-PET/CT. A comparison in the ability to identify active disease was performed between the established Kerr score and the new 18F-FDG-PET/CT was also performed.

Objectives: To investigate the utility of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) in assessing disease activity in TA.

Methods: Ninety-one patients with TA, were recruited from a Chinese cohort from October 2017 to January 2019. Clinical data, acute-phase reactants (APRs), and 18F-FDG-PET/CT findings were simultaneously recorded. The Physician Global Assessment was used as the gold standard to assess TA disease activity. The value of using 18F-FDG-PET/CT to identify active disease was evaluated, using erythrocyte sedimentation rate (ESR) as a reference. Disease activity assessment models were constructed and concordance index (C-index), net reclassification index (NRI), and integrated discrimination index (IDI) were evaluated to compare the benefits of the new modes with ESR and Kerr score.

Results: In total, 64 (70.3%) cases showed active disease. Higher levels of ESR and CRP, and lower interleukin (IL)-2R levels, were observed in active cases. 18F-FDG-PET/CT parameters, including SUVmean, SUVratio1, SUVratio2, sum of SUVmean, and sum of SUVmax, were significantly higher in active disease groups. The C index threshold of ESR to indicate active disease was 0.78 (95% CI: 0.69-0.88). The new activity assessment model combining ESR, sum of SUVmean, and IL-2R showed significant improvement in C index over the ESR method (0.96 vs. 0.78, P < 0.01; NRI 1.63, P < 0.01; and IDI 0.48, P < 0.01). The new model also demonstrated modest superiority to Kerr score assessment (0.96 vs. 0.87, P = 0.03; NRI 1.19, P < 0.01; and IDI 0.33 P < 0.01).

Conclusion: A novel 18F-FDG-PET/CT-based method that involves combining the sum of SUVmean with ESR score and IL-2R levels demonstrated superiority in identifying active TA compared to conventional methods.

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Disclosure of Interests: None declared