18F-Fludeoxyglucose PET/CT in the evaluation of large-vessel vasculitis: diagnostic performance and correlation with clinical and laboratory parameters.

OBJECTIVE

To investigate the diagnostic performance of (18)F-fludeoxyglucose ((18)F-FDG) positron emission tomography (PET)/CT in patients with suspected large-vessel vasculitis and its potential to evaluate the extent and activity of disease.

METHODS

78 consecutive patients (mean age 63 years; 53 females) with suspected large-vessel vasculitis were evaluated with (18)F-FDG PET/CT.( 18)F-FDG uptake in the aorta and major branches was visually graded using a four-point scale and quantified with standardised uptake values (SUV(max)). According to clinical diagnosis, patients were classified into three groups: (a) steroid-naïve, large-vessel vasculitis (16 patients), (b) vasculitis on steroid treatment (18 patients) and (c) no evidence of vasculitis (44 patients). Analysis of variance and linear regression were used to investigate the association of (18)F-FDG uptake with clinical diagnosis and inflammatory markers.

RESULTS

(18)F-FDG PET/CT was positive (visual uptake ≥ 2; equal to or greater than liver) in all patients with steroid-naïve, large-vessel vasculitis. The thoracic aorta, the carotid and the subclavian arteries were most frequently involved. In these patients, SUV(max) values were significantly higher than in the other groups (analysis of variance; p<0.05). Linear regression showed a significant positive association (b-coefficients: 0.018-0.02; p<0.05) between SUV(max) of the thoracic aorta and inflammatory markers in patients with vasculitis (Groups a and b). Patients on steroid treatment showed low visual scores (uptake <2) and significantly lower SUV(max) values than steroid-naïve patients.

CONCLUSION

(18)F-FDG PET/CT can detect the extent and activity of large-vessel vasculitis in untreated patients and is unreliable in diagnosing vasculitis in patients on steroids.