An increased major vessel uptake by 18F-FDG-PET/CT in NIH criteria inactive patients with Takayasu's arteritis.

OBJECTIVES: The commonly adopted method of defining active disease in Takayasu's arteritis (TAK) is the definition used by the US National Institutes of Health (NIH). A gold standard in imaging techniques for assessing disease activity in TAK has not been clearly established and the creation of practical and valid tools represents a challenge. To assess whether 18F-FDG-PET/CT and NIH criteria show a good level of agreement in assessing disease activity of TAK patients. METHODS: 18F-FDG-PET/CT was performed in 17 patients with TAK. All 17 patients fulfilled the clinical criteria according to the American College of Rheumatology criteria. Two nuclear physicians visually assessed the degree of 18F-FDG uptake in the inflammatory vascular lesion. 18F-FDG-PET/CT and the inflammatory vascular lesion were evaluated by using the standardised uptake value (SUV) of 18F-FDG accumulation were interpreted as active vasculitic lesions. RESULTS: Of the 17 patients, 6 were in the active stage and 11 were in the inactive stage according to the level of disease activity as clinically assessed by the NIH criteria. No significant 18F-FDG accumulation was observed in the patients with inactive disease (SUV≤1.2). 18F-FDG-PET/CT localised 18F-FDG accumulation in the inflammatory lesion in the patients with TAK who had inactive disease (n=3) assessed by the NIH criteria. 18F-FDG PET/CT revealed intense 18F-FDG accumulation (SUV max 2.88) in the vasculature of 3 patients in the inactive stage of TAK. The other 8 patients in the active stage showed weak 18F-FDG accumulation (SUV ≤1.2). CONCLUSION: 18FDG-PET/CT appears to be a promising technique for the diagnosis and assessment of disease activity in patients of TAK, even those considered to be inactive by the NIH criteria. However, it needs to be validated in larger groups for cost-effectiveness and sensitivity to change.