Predictors of infectious foci on FDG PET/CT in Staphylococcus aureus bacteremia

Abstract

Purpose: To identify risk factors for detection of infectious foci on 18F-fluorodeoxyglucose-positron emission tomography in combination with computed tomography(FDG PET/CT) among patients with Staphylococcus aureus bacteremia (SAB). Methods: Cohort study of patients with SAB who underwent FDG PET/CT as part of an interventional study that was conducted at Rambam Health Care Campus, between July 1, 2015 to February 1, 2019. The primary outcome was an infectious focus detected by FDG PET/CT. Independent risk factors for detection of focal infection were identified using univariate followed by a logistic regression multivariate analysis. Results: We included 149 patients with 151 separate episodes of SAB who underwent FDG-PET/CT. Focal infections were detected in 107 patients (70.8%). Independent risk factors for focal infection detection were community acquisition of bacteremia with odds ratio (OR) 3.03 [95% confidence interval (CI) 1.04-8.77], p-0.042 and C reactive protein (CRP) with OR 1.09 [ 95% CI 1.04-1.14], p<0.001. Primary bacteremia was inversely associated with focal infection detection with OR 0.27 [0.10-0.69], p=0.007, as were the pre-scan blood glucose levels OR 0.9 [0.98-0.99], p-0.004. The latter stayed significant in the subgroup of patients with diabetes mellitus. Conclusion: Patients with community-acquired bacteremia or high CRP levels should be carefully investigated for focal infection. Patients who present with primary bacteremia seems to be at low risk for focal infection. Further studies should evaluate whether high glucose levels may result in false-negative infectious findings on FDG PET/CT.