• Alison H Clifford, Elana M Murphy, Steven C Burrell, Mathew P Bligh, Ryan F MacDougall, J Godfrey Heathcote, Mathieu C Castonguay, Min S Lee, Kara Matheson, and John G Hanly.
• From the Division of Rheumatology, Department of Medicine, and the Department of Diagnostic Imaging, and the Division of Anatomic Pathology, Department of Pathology and Laboratory Medicine, and the Division of Vascular Surgery, Department of Surgery, Queen Elizabeth II Health Sciences Centre, Nova Scotia Health Authority; Dalhousie University, Halifax; Department of Radiology, Valley Regional Hospital, Kentville, Nova Scotia; Division of Rheumatology, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada. alison5@ualberta.ca.
• J Rheumatol. 2017 Dec 1; 44 (12): 1859-1866.

ObjectiveLarge vessel uptake on positron emission tomography/computerized tomography (PET/CT) supports the diagnosis of giant cell arteritis (GCA). Its value, however, in patients without arteritis on temporal artery biopsy and in those receiving glucocorticoids remains unknown. We compared PET/CT results in GCA patients with positive (TAB+) and negative temporal artery biopsies (TAB-), and controls.MethodsPatients with new clinically diagnosed GCA starting treatment with glucocorticoids underwent temporal artery biopsy and PET/CT. Using a visual semiquantitative approach, 18F-fluorodeoxyglucose (FDG) uptake was scored in 8 vascular territories and summed overall to give a total score in patients and matched controls.ResultsTwenty-eight patients with GCA and 28 controls were enrolled. Eighteen patients with GCA were TAB+. Mean PET/CT scores after an average of 11.9 days of prednisone were higher in patients with GCA compared to controls, for both total uptake (10.34 ± 2.72 vs 7.73 ± 2.56; p = 0.001), and in 6 of 8 specific vascular territories. PET/CT scores were similar between TAB+ and TAB- patients with GCA. The optimal cutoff for distinguishing GCA cases from controls was a total PET/CT score of ≥ 9, with an area under the receiver-operating characteristic curve of 0.75, sensitivity 71.4%, and specificity 64.3%. Among patients with GCA, these measures correlated with greater total PET/CT scores: systemic symptoms (p = 0.015), lower hemoglobin (p = 0.009), and higher platelet count (p = 0.008).ConclusionVascular FDG uptake scores were increased in most patients with GCA despite exposure to prednisone; however, the sensitivity and specificity of PET/CT in this setting were lower than those previously reported.

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