Diagnosing patients with polymyalgia rheumatica, giant cell arteritis, or both may be helped by using a specialized type of imaging that combines positron emission tomography and computed tomography.
For patients with clinical suspicion of polymyalgia rheumatica, giant cell arteritis, or both, fluorine‐18‐fluorodeoxyglucose (18F‐FDG) positron emission tomography/computed tomography (PET/CT) imaging offers value, according to a study published online in ACR Open Rheumatology.
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“18F‐FDG PET/CT is a powerful imaging technique in polymyalgia rheumatica and giant cell arteritis that was in good agreement with clinical diagnosis and temporal artery biopsy,” the researchers wrote.
The prospective, observational study included 80 participants with suspected polymyalgia rheumatica, giant cell arteritis, or concomitant polymyalgia rheumatica and giant cell arteritis. Participants underwent 18FDG‐PET/CT scans before or within 3 days of initiation of steroids in the case of giant cell arteritis and were followed for 40 weeks.
According to the study, 80% of participants were diagnosed with pure polymyalgia rheumatica, 3.7% with pure giant cell arteritis, and 12.5% with concomitant polymyalgia rheumatica and giant cell arteritis. During follow-up, 3.7% of participants were diagnosed with seronegative rheumatoid arthritis.
18F‐FDG PET/CT imaging had a proportion of agreement of 75.3 compared with clinical diagnosis for polymyalgia rheumatica, the researchers reported. In addition, 18F‐FDG PET/CT had a proportion of agreement of 93.0 with temporal artery biopsy in all participants and 69.2 in a subgroup of participants with vasculitis.
C‐reactive protein was significantly higher in participants with polymyalgia rheumatica activity on 18F‐FDG PET/CT compared with those without activity, the researchers said.
“18F‐FDG PET/CT can also help with the diagnostic workup of polymyalgia rheumatica and giant cell arteritis patients to rule out other mimics of the disease, especially in the case of polymyalgia rheumatica,” they wrote. “However, particular attention should be paid to the patients with individual inflammation in the cranial arteries, in which the sensitivity of 18F‐FDG PET/CT is influenced by the small diameter of these vessels, though with excellent specificity.”
Emamifar A, Ellingsen T, Hess S, et al. 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. ACR Open Rheumatol. Published online July 22, 2020. doi:10.1002/acr2.11163