Giant cell arteritis (GCA) is the most frequent form of vasculitis in persons older than 50 years. Cranial and systemic large vessels can be involved. [18F] fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) is increasingly used to diagnose inflammation of the large arteries in GCA. Unfortunately, no consensus exists on the preferred scoring method. In the present study, we aim to define the optimal FDG PET/CT scoring method for GCA diagnosis using temporal artery biopsy and clinical diagnosis as the reference method.FDG PET/CT scans of GCA patients (12 glucocorticoid-naive, 6 on glucocorticoid treatment) and 3 control groups (inflammatory, atherosclerotic, and normal controls) were evaluated. We compared 2 qualitative visual methods (i.e. (1a) first impression and (1b) vascular uptake versus liver uptake) and 4 semiquantitative methods ((2a) SUVmax aorta, (2b) SUVmax aorta-to-liver ratio, (2c) SUVmax aorta-to-superior-caval-vein ratio, and (2d) SUVmax aorta-to-inferior-caval-vein ratio). FDG uptake pattern (diffuse or focal) and presence of arterial calcifications were also scored.Diagnostic accuracy of the visual method vascular versus liver uptake (1b) was highest when the cut-off point “vascular uptake higher than liver uptake” (sensitivity 83%, specificity 91%) was used. Sensitivity increased to 92% when patients on glucocorticoids were excluded from the analysis. Regarding the semiquantitative methods, the aorta-to-liver ratio (2b) with a cutoff of 1.03 had the highest diagnostic accuracy, with a sensitivity and specificity of 69% and 92%, respectively. Sensitivity increased to 90% when patients on glucocorticoids were excluded. The number of vascular segments with diffuse FDG uptake pattern was significantly higher in GCA patients without glucocorticoid use compared with all control patient groups. CRP was not significantly different between positive and negative FDG PET scans in the GCA group.Visual vascular uptake higher than liver uptake resulted in the highest diagnostic accuracy for the detection of GCA, especially in combination with a diffuse FDG uptake pattern. Of the semiquantitative methods, the aorta-to-liver SUVmax ratio (cutoff point = 1.03) had the highest diagnostic accuracy. The diagnostic accuracy increased when patients using glucocorticoids were excluded from the analyses.

BackgroundGiant cell arteritis (GCA) is the most frequent form of vasculitis in persons older than 50 years. Cranial and systemic large vessels can be involved. [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET)/ computed tomography (CT) is increasingly used to diagnose inflammation of the large arteries in GCA. Unfortunately, no consensus exists on the preferred scoring method.ObjectivesIn the present study, we aim to define the optimal scoring method for GCA for FDG PET/CT, using temporal artery biopsy and clinical diagnosis as the reference method.MethodsFDG PET/CT scans of GCA patients (glucocorticoid-naïve n=12, on glucocorticoid treatment n=6) and 3 control groups (inflammatory n=18, atherosclerotic n=19, normal controls n=16) were evaluated. We compared two qualitative visual methods (i.e. (1a) first impression and (1b) vascular uptake versus liver uptake) and four semi-quantitative methods ((2a) SUVmax aorta, (2b) SUVmax aorta-to-liver ratio, (2c) SUVmax aorta-to-superior-caval-vein ratio and (2d) SUVmax aorta-to-inferior-caval-vein ratio). FDG uptake pattern (diffuse or focal) and presence of arterial calcifications were also scoredResultsAccuracy of the visual method vascular versus liver uptake was highest when using the cut-off point “vascular uptake higher than liver uptake” (sensitivity 83%, specificity 91%). Sensitivity increased to 92% when patients on glucocorticoids were excluded from the analysis. Regarding the semi-quantitative methods, the SUVmax aorta-to-liver cut-off ratio had the highest accuracy. The optimal cut-off point was 1.03, with sensitivity being 69% and specificity 92%. Sensitivity increased to 90% when excluding patients on glucocorticoids. The number of vascular segments with diffuse uptake pattern was significantly higher in GCA patients without glucocorticoid use compared with all control patient groups. CRP was not significantly different between positive and negative FDG PET scans in the GCA group.ConclusionsVisual vascular uptake higher than liver uptake resulted in the highest accuracy for the detection of GCA, especially in combination with a diffuse uptake pattern. An aorta-to-liver SUVmax ratio higher than 1.03 had the highest accuracy as semi-quantitative method. The accuracy increased when excluding patients using glucocorticoids from the analyses.AcknowledgementsWe received a special grant from the NC Smit/Dutch Arthritis Association for our GCA cohort.Disclosure of InterestNone declared

BackgroundPatients with rheumatoid arthritis (RA) have an elevated risk of developing cardiovascular disease (CVD). Like RA, atherosclerosis is a chronic inflammatory process. There are indications that aortic inflammation in atherosclerosis can be detected by 18F-Fluorodeoxyglucose-positron emission tomography/computed tomography (18F-FDG-PET/CT).ObjectivesTo quantify 18F-FDG uptake in large arteries of RA patients as compared to controls using PET/CT as a potential marker of vascular wall inflammation in areas of atherosclerosis, and its association with disease activity in patients with RA.Methods18F-FDG-PET/CT studies were performed in patients with active early RA (DAS28 >4.0; median disease duration 12 (8 – 21) days; n=20), active established RA (DAS28 >4.0; median disease duration 8 (3 – 14) years; n=23) and in controls with osteoarthritis (OA; n=15). Semi-quantitative FDG-uptake in the arterial walls was determined by standardized uptake values (SUV) and tissue-to-background ratios (TBR) using 18F-FDG activity in the vena cava as background. Volumes of interest (VOI) covering an arterial segment were defined to derive the maximum SUV (SUVmax, regional arterial uptake). Global arterial uptake was estimated by using the mean of all regional arterial uptakes in all arteries.ResultsRegional as well as global arterial uptake of 18F-FDG was the highest in patients with early RA as compared to established RA and OA, with significantly higher SUV in the thoracic aortic tract (respectively p=0.009 and p=0.005), the abdominal aorta (respectively p=0.031 and p=0.005) and the femoral arteries (respectively p=0.136 and p=0.016). SUV didn't differ significantly between established RA an OA controls (data not shown). C-reactive protein (CRP) levels were associated with increased global arterial SUV (β=1.15, 95% CI 1.07 – 1.24; P=0.003) as well as increased regional arterial SUV in the thoracic aortic tract (β=1.18, 95% CI 1.06 – 1.30; P=0.006), the iliac arteries (β=1.11, 95% CI 1.03 – 1.19; P=0.016) and the femoral arteries (β=1.18, 95% CI 1.07 – 1.30; P=0.006) in early RA patients and not in established RA (data not shown). DAS28 levels were only associated with SUV levels in early RA (global arterial uptake β=0.162, 95% CI 0.032 – 0.292; P=0.018, thoracic aortic tract β=0.189, 95% CI 0.042 – 0.335; P=0.015, iliac arteries β=0.134, 95% CI 0.012 – 0.257; P=0.034, femoral arteries β=0.164, 95% CI 0.007 – 0.321; P=0.041). There were no significant differences in TBR between both RA groups and OA (data not shown).ConclusionsIncreased and predominantly regional vascular wall uptake of 18F-FDG as sign of vascular inflammation was found in several arterial segments of early RA patients, suggesting atherosclerosis, and was associated with clinical assessments of disease activity. The lack of differences between the established RA and OA controls and the lack of differences in TBR requires further study.Disclosure of InterestNone declared