The Utility of 18F-FDG PET/CT in Patients With Clinical Suspicion of Polymyalgia Rheumatica and Giant Cell Arteritis: A Prospective, Observational, and Cross-sectional Study.

OBJECTIVE: To define the proportions of agreement between fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT), clinical diagnosis, and temporal artery biopsy (TAB) in patients with polymyalgia rheumatica (PMR) and giant cell arteritis (GCA). Furthermore, the association of 18F-FDG PET/CT uptake patterns and clinical presentation of newly diagnosed PMR and GCA was investigated.

METHODS: Eighty patients newly suspected of having PMR, GCA, or concomitant PMR and GCA were included and followed for 40 weeks. Every patient underwent an 18F-FDG PET/CT scan before or within 3 days of initiation of steroids in case of GCA. FDG uptakes in 8 paired articular/periarticular sites and 14 arterial segments were evaluated based on a 4-point visual grading scale.

RESULTS: Of the 80 patients (female: 50 [62.5%]; mean age ± SD: 72.0 ± 7.9), 64 (80.0%) patients were diagnosed with pure PMR, 3 (3.7%) with pure GCA, and 10 (12.5%) with concomitant PMR and GCA. Additionally, three (3.7%) patients were diagnosed with seronegative rheumatoid arthritis during the follow-up period. For the diagnosis of PMR, 18F-FDG PET/CT had a proportion of agreement of 75.3 (64.2-84.4), compared with clinical diagnosis. When comparing findings of 18F-FDG PET/CT with TAB, 18F-FDG PET/CT had a proportion of agreement of 93.0 (84.3-97.7) in all included patients and 69.2 (38.6-90.9) in the subgroup of patients with vasculitis. C-reactive protein was significantly higher in patients with PMR activity on 18F-FDG PET/CT compared with those without 18F-FDG PET/CT activity (P value = 0.006).

CONCLUSIONS: 18F-FDG PET/CT is a powerful imaging technique in PMR and GCA that was in good agreement with clinical diagnosis and TAB.