AB0597 FDG PET-CT versus Temporal Artery Biopsy in Patients Presenting with Gca/Pmr: A Retrospective Cross-Sectional Study
Authors: S.A. Just, R.A. Gildberg-Mortensen, R.A. Andreasen, N. Lomborg, M.B. Morillon, I.M.J. Hansen
Journal: Annals of the Rheumatic Diseases (2014)

<h3>Background</h3> Giant Cell Arteritis (GCA) is a large vessel vasculitis, which can occur concomitant with Polymyalgia Rheumatica (PMR). Both diseases may also be seen as isolated disease entities. The two conditions are treated differently, and therefore correct diagnosis is essential. Positron-emission tomography (PET) using <sup>18</sup>F-fluorodeoxyglucose (FDG) is receiving increasing attention in the diagnostics of both GCA and PMR (1, 2). In GCA FDG uptake is often seen in the large vessels of the thorax and neck – hereafter called vasculitis pattern (1). In isolated Polymyalgia Rheumatica (PMR) uptake can be seen in the ischial tuberosities, the greater trochanters, and the lumbar spinous processes – hereafter called PMR pattern (3). Temporal artery biopsy is part of the diagnostic workup when GCA is suspected, confirming the diagnosis if characteristic vasculitis histology is found. <h3>Objectives</h3> To describe the sensitivity and specificity of vascular FDG uptake on PET-CT compared to temporal artery biopsy result, in suspected GCA and/or PMR. <h3>Methods</h3> In a cross-sectional retrospective study design, all patients with the diagnosis GCA and/or PMR attending our rheumatologic ambulatory as of 1 of December 2013 were included. At time of disease presentation, temporal artery biopsy description, treatment start, date of FDG PET-CT and description were registered. Patients were classified according to arterial biopsy (normal or vasculitis) and PET-CT FDG uptake pattern (normal, PMR or vasculitis). If there was FDG uptake in the major vessels, this classified as vasculitis pattern, regardless of coexisting PMR pattern. <h3>Results</h3> Information about 118 patients was retrieved. 83 of these had been diagnosed with isolated PMR, and 36 with GCA with or without PMR. 32 patients had undergone both FDG PET-CT scan and temporal artery biopsy at presentation (19 PMR and 13 GCA). The following PET-CT FDG uptake patterns were found: 5 Normal, 15 with PMR and 12 with vasculitis. Three with biopsy verified vasculitis had received glucocorticoids before PET-CT (1 with vasculitis pattern, 1 PMR pattern and 1 normal). Table 1 relates the temporal biopsy description with PET-CT FDG uptake pattern. PET-CT FDG vasculitis uptake had a sensitivity of 78% (7/9) and a specificity of 78% (18/23). The positive and negative predictive value was 58% (7/12) and 90% (18/20), respectively. <h3>Conclusions</h3> This study shows that FDG PET-CT, as a measure of vascular involvement in suspected GCA and/or PMR, should be used with caution. <h3>References</h3> Blockmans D. PET in vasculitis. Annals of the New York Academy of Sciences. 2011 Jun;1228:64-70. Hooisma GA, Balink H, Houtman PM, Slart RH, Lensen KD. Parameters related to a positive test result for FDG PET(/CT) for large vessel vasculitis: a multicenter retrospective study. Clinical rheumatology. 2012 May;31(5):861-71. Yamashita H, Kubota K, Takahashi Y, Minaminoto R, Morooka M, Ito K, et al. Whole-body fluorodeoxyglucose positron emission tomography/computed tomography in patients with active polymyalgia rheumatica: evidence for distinctive bursitis and large-vessel vasculitis. Modern rheumatology/the Japan Rheumatism Association. 2012 Sep;22(5):705-11. <h3>Acknowledgements</h3> Just S.A and Gildberg-Mortensen R. contributed equally to this work. <h3>Disclosure of Interest</h3> None declared <h3>DOI</h3> 10.1136/annrheumdis-2014-eular.2284