Patient characteristics
Between January 2007 and Juni 2009 we screened 85 patients with different forms of uveitis by QuantiFERON TB-Gold test. Positive test results were found in 24 patients. The types of intraocular inflammation in the QuantiFERON positive patients were retinal vasculitis, serpiginous choroiditis, multifocal choroiditis, anterior and posterior uveitis and panuveitis.
Nine patients were female and 15 patients male. The mean age of the patients was 51 years (range 17-76 years). Details of patient characteristics are summarized in Table 1.
PET/CT examination
18F-FDG-PET/CT was performed in 20 of the QuantiFERON positive patients. Three patients refused PET/CT and in one patient with enlarged but metabolically inactive mediastinal lymph nodes PET/CT was not performed.
Before the PET/CT examination all 24 QuantiFERON positive patients underwent extensive clinical workup, including chest X-ray (17 patients) or CT (7 patients). Chest X-ray and CT did not reveal any abnormalities in 21 QuantiFERON positive patients.
The protocol of the PET/CT examination was a standard one with 60 minutes uptake time after administration of 350 MBq 18F-FDG. The examinations were performed with a modern PET/CT scanner consisting of a high-resolution 3D LSO PET and a 16-row multi-detector CT. All FDG-PET/CT scans included a contrast-enhanced CT to obtain diagnostic CT data (Figure 2).
Analysis of PET/CT data
PET/CT images were carefully evaluated for the presence, size and metabolic activity of hilar and/or mediastinal lymph nodes and pulmonary lesions. FDG uptake was evaluated visually as well as semi-quantitatively (SUVmax, maximum standard uptake value).
PET: Any focal, even faint FDG uptake in a normal-sized or enlarged lymph node exceeding normal regional tracer accumulation was regarded “PET positive” (= metabolically active lymph node) and indicative for inflammatory lesions (including TB) (Figure 3, Figure 4). Lymph nodes without FDG uptake were classified as “PET negative” (= metabolically inactive lymph nodes).
CT: The presence of calcified or non-calcified, normal-sized or (slightly) enlarged mediastinal or hilar lymph nodes with or without additional granulomas in the lung were regarded as “CT positive” for inflammatory lesions (including TB) (Figure 5, Figure 6).
For semi-quantitative analysis (SUV) of PET data a three-dimensional regions of interest (ROI) was placed over the FDG avid lymph node, semi-automatically, using a dedicated software program with a threshold of 50% of the maximum tracer uptake. The maximum standard uptake value (SUVmax) was calculated from each ROI according to the formula: SUV = measured activity concentration (Bq/ml)/injected activity (Bq) per body volume (ccm).
Bronchoscopy
If technically possible, bronchoscopy with PET/CT guided transbronchial biopsy of the suspicious lymph nodes was performed.
Tuberculostatic treatment
In QuantiFERON positive patients with progressive and sight-threatening course and positive PET/CT results an anti-tuberculosis treatment was instituted.with a combination of three tuberculostatic agents (isoniazid, rifampicin and pyrazinamid) and systemic steroids for at least six months.