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Updated: May 14, 2025
An Immunohistopathologic Study to Profile the Folate Receptor Beta Macrophage and Vascular Immune Microenvironment in Giant Cell Arteritis
Published on: February 8, 2019
Use of fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography in diagnosing giant cell
Madeleine Venables1, Andrew Taylor1, Julia Murdoch1
1Department of Rheumatology, Royal Perth Hospital, Perth, Western Australia, Australia.
Background:
Fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) has been established as a beneficial diagnostic tool in large vessel vasculitis. There have been limited studies of its use in real-world clinical practice. We examined patients at Royal Perth Hospital (RPH) with suspected giant cell arteritis (GCA) from January 2019 to 2022 who had 18F-FDG-PET/CT, and analysed its diagnostic accuracy compared to temporal artery biopsy (TAB) and clinical diagnosis at 6 months.
Methods:
Patients referred to RPH Rheumatology with suspected GCA from January 2019 to 2022 were identified as having had 18F-FDG-PET/CT for diagnostic evaluation. 18F-FDG-PET/CT results were dichotomous into positive (consistent with GCA) or negative, and compared to TAB and clinical diagnosis of GCA at 6 months by a consultant rheumatologist.
Results:
A total of 32 patients had 18F-FDG-PET/CT for diagnostic purposes; nine of 32 18F-FDG-PET/CT scans were positive. Compared to TAB, 18F-FDG-PET/CT had a sensitivity of 50%, a specificity of 93%, a positive predictive value (PPV) of 86%, a negative predictive value (NPV) of 68% and accuracy of 61.5%. Compared to clinical diagnosis, 18F-FDG-PET/CT had a sensitivity of 41%, a specificity of 100%, a PPV of 100%, an NPV of 44% and accuracy of 59.4%. Only one 18F-FDG-PET/CT (11%) had cranial artery involvement. The median time taking glucocorticoids (GCs) was 7 days (interquartile range (IQR) 0-22.5 days) for positive 18F-FDG-PET/CT scans, versus 13 days (IQR 8-39 days) for negative 18F-FDG-PET/CT scans. The median time from request to scan was 29 days (IQR 31.5-77 days) for 18F-FDG-PET/CT on 14 or more days of GCs.
Conclusion:
18F-FDG-PET/CT is more likely to be positive if it is performed within 7 days of steroid commencement. 18F-FDG-PET/CT had lower sensitivity and higher specificity than reported in clinical studies. In clinical practice, the significant delays from steroid start to scan time may reduce diagnostic sensitivity. A negative 18F-FDG-PET/CT scan did not negate the need for further investigations.
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