Background 18F-Fluorodeoxyglucose (FDG) positron emission tomography/computerized tomography [PET/CT] is a useful tool to diagnose large vessel vasculitis (LVV) but its role in distinguishing between active and inactive disease is still debated.
Objectives To evaluate the utility of vascular standardized uptake value (SUV) assessment in differentiating between patients with clinical active and inactive LVV.
Methods All patients with LVV seen in our center undergo clinical, laboratory (ESR, CRP) and imaging assessment with PET/CT scans. We retrospectively compared 14 consecutive evaluations of 12 patients with active disease according to clinical indices ITAS (Indian Takayasu activity score) and Kerr/National Institute of Health (Kerr/NIH) with 15 evaluations of 10 patients with inactive disease. ITAS, Kerr/NIH scores, ESR and CRP values were obtained within 20 days from PET/CT scans. PET/CT scans were reviewed by two nuclear medicine physicians without any clinical information. Vascular uptake was assessed using visual 4-point semiquantitative scale, vascular max SUV and vascular max SUV/liver max SUV ratio (SUV ratio) in 12 vessel segments. The highest max SUV among the different vessel segments was used for the analysis.
Results Patients with active disease according to ITAS and Kerr/NIH indices compared to patients with inactive disease had higher vascular max SUV (mean ± SD 4.31 ± 1.63 vs 2.89 ± 0.99 p= 0.008) and higher SUV ratio (1.71 ± 0,74 vs 1.1 ± 0.54 p=0.016).
Patients with visual grade >2 (high vascular uptake) compared to patients with visual grade <1 (low vascular uptake) had higher vascular max SUV (mean ± SD 4.62 ± 1.50 vs 2.6 ± 0.52 p< 0.0001) and SUV ratio (1.78 ± 0.78 vs 1.05 ± 0.41 p=0.004).
Correlations between max SUV and ESR or CRP (r = 0.551 p = 0.002 vs. ESR; r = 0.565 p = 0.001 vs. CRP) and between SUV ratio and ESR or CRP (r = 0.522 p = 0.004 vs. ESR; r = 0.586 p = 0.001 vs. CRP) were significant.
Conclusions Our results show higher values of max SUV and SUV ratio in active than in inactive LVV patients. Both max SUV and SUV ratio correlates significantly with ESR and CRP. The assessment of max SUV and SUV ratio is a promising tool in differentiating between active and inactive disease during follow-up of patients wit LVV.
Disclosure of Interest None Declared