18F-FDG PET/CT for Detection of Metastatic Infection in Gram-Positive Bacteremia

The timely detection of metastatic infectious foci in gram-positive bacteremia is crucial, because these foci often require prolonged antibiotic treatment or drainage. The diagnosis of metastatic infectious foci is difficult because localizing symptoms are often absent. We investigated whether 18F-FDG PET/CT was able to detect such foci and whether detection influenced clinical outcome. Methods: One hundred fifteen nonneutropenic patients with gram-positive bacteremia were prospectively included. PatientswithpositivebloodculturesgrowingStaphylococcus aureus, Streptococcus species, or Enterococcus species were eligiblewhenariskfactorfordevelopingmetastaticinfectiousfociwas present. 18 F-FDGPET/CTwasperformedwithin2wkafterthefirst positive blood culture. Abnormal 18 F-FDG uptake had to be confirmed by radiologic, microbiologic, or pathologic studies. Results were compared with a matched historical control group of 230 patients in whom no 18F-FDG PET/CT was performed. Results: Significantly more patients were diagnosed with metastatic foci in the study group (67.8% vs. 35.7%). Of the imaging investigations performed, 18 F-FDG PET/CT was the first to delineate infectious foci in 35 patients (30%). In the remaining 70%, either symptoms onphysicalexaminationorotherimagingtechniquesfirstrevealed infectious foci. The sensitivity, specificity, negative predictive value, and positive predictive value of 18 F-FDG PET/CT were 100%, 87%, 100%, and 89%, respectively. Relapse rates decreased from 7.4% to 2.6% among study patients (P 5 0.09) andfrom8.9%to1.4%inpatientswithS.aureus(P50.04).Overall mortality after 6 mo decreased from 32.2% to 19.1% in the 18 FFDG PET/CT group (P 5 0.014). Conclusion: In the diagnostic work-up of high-risk patients with gram-positive bacteremia, 18F