Session Title: Vasculitis
Session Type: Abstract Submissions (ACR)
Background/Purpose: Temporal artery (TA) biopsies are negative in up to 50% of patients with giant cell arteritis (GCA). In such cases, increased uptake in large arteries on PET/CT may support the clinical diagnosis. The objective of this study was to compare vascular (18F)-FDG uptake in patients with clinically diagnosed GCA to controls, and to compare uptake in GCA TA biopsy positive (TA+) patients to those with negative TA biopsies (TA-). Secondary outcomes evaluated the correlation of vascular uptake on PET/CT with clinical and laboratory variables and medications, including use of corticosteroids.
Methods: Patients with a clinical diagnosis of GCA and meeting ACR 1990 classification criteria were prospectively enrolled. Controls were identified from an oncology database, matched for age and sex. All GCA cases were treated per standard of care with high dose corticosteroids and underwent both TA biopsy and PET/CT. Using a 4 point scale, vascular FDG uptake was scored in 8 vascular territories and overall (total) by two nuclear medicine specialists, blinded to the clinical diagnosis. TA biopsies were interpreted by 2 anatomical pathologists with differences resolved by consensus. Statistical analysis used non-parametric Wilcoxon exact tests, Spearman correlations and analysis of variance.
Results: Twenty-eight patients with GCA (61% female, mean age ± SD: 70 ± 8.9 yrs) and 28 controls (61% female, 64 ± 8.2 yrs) were enrolled. TA biopsy was positive in 64% of GCA patients. Mean total PET/CT uptake scores were significantly higher in those with GCA (10.34 ± 2.72) compared to controls (7.73 ± 2.56, p=0.001.) Six of 8 vascular territories evaluated showed significantly greater uptake in GCA patients. TA+ and TA- GCA patients had similar total PET/CT uptake (10.86 ± 2.63 vs. 9.4 ± 2.76, p=0.2) and in each specific vascular territory. The optimal cut-off for distinguishing GCA cases from controls by total PET/CT uptake score was 9. This resulted in area under the curve of 0.75, with a sensitivity of 71.4% and specificity of 64.3%. The presence of systemic symptoms (p=0.015), lower hemoglobin levels (p=0.009) and higher platelet counts (p=0.008) were associated with higher PET/CT scores but ESR and CRP levels were not. The only association with corticosteroids was between higher daily dose adjusted for body weight with higher total PET/CT scores (p=0.033).
Conclusion: Large vessel disease was identified in the majority (71.4%) of GCA patients by PET/CT despite initiation of corticosteroids, with similar uptake noted in TA+ and TA- patients. The sensitivity of PET/CT was superior to that of TA biopsy for identification of patients with a clinical diagnosis of GCA. Systemic symptoms, in particular, were associated with greater total uptake scores.
J. G. Hanly,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/petct-for-the-diagnosis-of-giant-cell-arteritis-a-prospective-study/