AB1313 18F-FLUORODEOXYGLUCOSE-POSITRON EMISSION TOMOGRAPHY-COMPUTED TOMOGRAPHY FINDINGS OF POLYMYALGIA RHEUMATICA IN PATIENTS WITH LARGE VESSEL VASCULITIS
Authors: E. Heras-Recuero, M. Martínez de Bourio-Allona, L. C. Landaeta-Kancev, T. Blázquez-Sánchez, A. Torres-Roselló, M. Álvarez-Rubio, M. Belhaj-Gandar, L. Martínez-Dhier, J. A. Martinez-Lopez, R. Largo, M. A. Gonzalez-Gay
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Polymyalgia rheumatica (PMR) and giant cell arteritis (GCA) are common conditions in people older than 50 years from Western countries. The advent of new imaging techniques has been a great step forward for the diagnosis of GCA. Positron emission tomography-computed tomography (PET-CT) with 18F-fluorodeoxyglucose (18F-FDG) is one of the imaging techniques that has made it possible to identify GCA patients with a predominantly extracranial LVV pattern of the disease. An issue that from our point of view has been less evaluated is the usefulness of 18F-FDG-PET-CT to identify PMR in patients diagnosed with LVV-GCA. To address this question and determine the best predictors of 18F-FDG-PET-CT to clinically identify PMR in patients with LVV-GCA, we evaluated a cohort of patients diagnosed with LVV-GCA using 18F-FDG-PET-CT. <h3>Objectives:</h3> Polymyalgia rheumatica (PMR) and giant cell arteritis (GCA) are often overlapping conditions. We aimed to determine whether 18F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) is useful in identifying PMR in the setting of large vessel vasculitis (LVV)-GCA. <h3>Methods:</h3> Patients diagnosed with LVV-GCA by PET-CT at a tertiary referral hospital for a population of 450,000 people over a two-year period were reviewed. Scoring was performed based on potential significant FDG uptake at up to 16 sites in nine different extravascular areas (SCORE 16). Differences in extravascular sites of significant FDG uptake were evaluated between LVV-GCA with a clinical diagnosis of PMR or not. <h3>Results:</h3> Fifty-four patients were diagnosed with LVV-GCA by 18F-FDG-PET-CT. Of them, 21 (38.8%) were clinically diagnosed with PMR. Significant extravascular FDG uptake was more frequently observed in those with a clinical diagnosis of PMR. In this sense, the SCORE 16 was higher in those with clinical PMR (5.10 ± 4.05 versus 1.73 ± 2.31 in those without a clinical diagnosis of PMR; p&lt; 0.001). A SCORE 16 involving more than 4 sites of significant FDG uptake yielded a sensitivity of 52% and a specificity of 91% for establishing a clinical diagnosis of PMR associated with LVV-GCA. The best areas of significant FDG uptake to clinically identify PMR in patients with LVV were the shoulder, the greater trochanter and the lumbar interspinous regions with an area under the ROC curve of 0.810 (0.691-0.930). <h3>Conclusion:</h3> Significant extravascular 18F-FDG-PET-CT uptake may help establish a clinical diagnosis of PMR in patients with LVV-GCA. These patients are more commonly diagnosed with PMR if they have significant FDG uptake in the shoulder, greater trochanter, and lumbar interspinous areas. <h3>REFERENCES:</h3> <b>NIL.</b> <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> <b>None declared.</b>