Division of Angiology, Department of Internal Medicine, University Hospital Graz, Auenbruggerplatz 15, 8036 Graz, Austria
Correspondence to: M. Brodmann. E-mail: marianne.brodmann{at}kfunigraz.ac.at
I read with great interest your response to our article. In fact it was not surprising that 18FDG PET is not suitable for the diagnosis of temporal arteritis due to the limited spatial resolution of the PET scanners that are commercially available at present. However, the aim of the study was to emphasize this point and to make a clear statement in a relatively large patient group that 18FDG PET is not suitable as a non-invasive diagnostic procedure in patients with temporal arteritis and cannot replace invasive biopsy as one of the ACR criteria.
You noted that only eight out of 22 patients had temporal artery biopsy, and therefore a definitive correlation with a pathological gold standard was provided in only 36% of cases, in your opinion. In fact it was eight patients out of 17 patients, all of whom had shown the positive halo in duplex sonography as a sign of temporal artery involvement in giant cell arteritis. As the literature records positive histological findings in temporal arteritis in only 5070% of cases in which biopsy is done, due to the segmental occurrence of giant cell arteritis, the correlation in our data does not seem so bad. Furthermore, as we performed another study (M. Brodmann, G. Seinost, E. Pabst, M. Tarmann and E. Pilger, submitted for publication) looking for the correlation of biopsy and duplex sonography, where we did not see histologically proven temporal arteritis when duplex sonography was negative (halo <1 mm).
I completely agree that there may be a certain bias in our study, as all patients were diagnosed according the ACR criteria, and that this may be a reason for the high correlation of positive 18FDG PET scans and duplex sonographic findings in the large vessels.
I also completely agree that, in patients with unclear symptoms who have not necessarily met the ACR criteria, a positive whole-body 18FDG PET scan can prevent time-consuming diagnostic procedures and valuable time loss before treatment is started. This is, in my opinion, the patient population who can benefit most from this diagnostic procedure.
In conclusion, I would like to agree with you that at present there is no perfect method for the diagnosis of giant cell arteritis, but that a lot of procedures, such as 18FDG PET scanning and duplex sonography, can be a great help, especially in skilled hands and when the symptoms are unclear. Furthermore, one important aspectthe possibility of monitoring an inflammatory process with 18FDG PET scanningshould also not be forgotten.
Accepted 7 November 2003