Background Disease activity (DA) assessment in Takayasu arteritis (TA) is an unresolved enigma as systemic inflammation and current activity measures poorly correlate with arterial progression. Morphological imaging, e.g. with morphological magnetic resonance (MR) sequencies, is the goal standard to evaluate arterial progression after its occurrence, and it is not clear whether functional characterisation of the lesions (e.g. contrast enhancement at MR or fluorodesoxyglucose [FDG] uptake at FDG-PET/CT [PET]) can predict arterial progression before its occlusion. We are prospectively following 60 TA patients with functional and morphological imaging to understand the predictors of arterial progression. Here we present the baseline assessment of the first 47 patients.
Objectives to verify if activity measures, and functional lesion characterisation with PET or MR provide independent information.
Methods Cross-sectional analysis of 47 TA patients according to ACR criteria followed at our Institution and undergoing closely related MR, PET and clinical evaluation. DA was evaluated with NIH criteria, indian Takayasu activity score (ITAS2010) and physician global assessment (PGA). At MR, arterial lesions were characterized by length, thickness and percentage of stenosis. Contrast to noise ratio (CNR) was calculated, when technically possible. Each vascular lesion uptake large enough to be evaluated by PET was evaluated with a quantitative (SUVmax) method. Per patients and per lesion analyses were performed.
Results The median interval between MR and PET was 24 days. TA was active in 25, 17 and 35 patients according to NIH criteria, ITAS2010 and PGA (including active and grumbling disease). In total, MR identified 333 arterial lesions (median lesion N per patient 6, IQR 1–15). At the “per patient” analysis, median CNRmax at MR was 12,43 (IQR 0,00–54,29). CNRmax did not correlate with acute-phase markers nor activity measures, except for ITAS-CRP (rho 0.300, p=0,038). PET showed significant uptake in 18 patients. Meadian SUVmax was 1,19 (IQR 0,00–9,00). SUVmax did not correlate with activity measures.
At the “per lesions” analysis, 56 lesions had positive uptake in PET. There was no correlation between the degree of enhancement at MR and of FDG uptake at PET (rho 0,094, p=0,529).
Conclusions Current activity measures, mainly based on systemic inflammation, and functional characterisation of the arterial lesions by MR and FDG-PET provide independent information in TA. The prospective part of this study will clarify the clinical relevance and the predictive values for progression of these different pieces of information.
Disclosure of Interest None declared