Introduction.18F-FDG-PET visualises inflammation. Both atherosclerosis and giant cell arteritis cause vascular inflammation, but distinguishing the two may be difficult. The goal of this study was to assess interobserver agreement and diagnostic accuracy of18F-FDG-PET for the detection of large artery involvement in giant cell arteritis (GCA).Methods. 3118F-FDG-PET/CT scans were selected from 2 databases. Four observers assessed vascular wall18F-FDG uptake, initially without and subsequently with predefined observer criteria (i.e., vascular wall18F-FDG uptake compared to liver or femoral artery18F-FDG uptake). External validation was performed by two additional observers. Sensitivity and specificity of18F-FDG-PET were determined by comparing scan results to a consensus diagnosis.Results. The highest interobserver agreement (kappa: 0.96 in initial study and 0.79 in external validation) was observed when vascular wall18F-FDG uptake higher than liver uptake was used as a diagnostic criterion, although agreement was also good without predefined criteria (kappa: 0.68 and 0.85). Sensitivity and specificity were comparable for these methods. The criterion of vascular wall18F-FDG uptake equal to liver18F-FDG uptake had low specificity.Conclusion. Standardization of image assessment for vascular wall18F-FDG uptake promotes observer agreement, enables comparative studies, and does not appear to result in loss of diagnostic accuracy compared to nonstandardized assessment.
Clinical implication of FDG-PET/CT in monitoring disease activity in large-vessel giant cell arteritis linked with secondary polymyalgia rheumatica
