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FDG-PET/CT for Detecting an Infection Focus in Patients With Bloodstream Infection

Factors Affecting Diagnostic Yield

Pijl, Jordy P., BSc*; Glaudemans, Andor W. J. M., MD, PhD*; Slart, Riemer H. J. A., MD, PhD*†; Yakar, Derya, MD, PhD*; Wouthuyzen-Bakker, Marjan, MD, PhD; Kwee, Thomas C., MD, PhD*

doi: 10.1097/RLU.0000000000002381
Original Articles

Purpose To investigate the diagnostic performance of 18F-fluoro-2-deoxy-D-glucose (FDG) PET/ CT for the detection of an infection focus in patients with a bloodstream infection (BSI) and to identify factors influencing the diagnostic yield of FDG-PET/CT.

Methods This retrospective single-center study included 185 consecutive patients with a BSI who underwent an FDG-PET/CT scan for the detection of an infection focus between 2010 and 2017. The final diagnosis at hospital discharge was used as reference standard. Diagnostic performance of FDG-PET/CT for the detection of an infection focus was assessed, and logistic regression analyses were performed to identify factors associated with FDG-PET/CT yield.

Results An infection focus was identified on FDG-PET/CT in 120 (64.8%) of 185 patients. FDG-PET/CT achieved a sensitivity of 80.2%, specificity of 79.6%, positive predictive value of 90.8%, and a negative predictive value of 61.4% for detecting an infection focus in patients with a BSI. Blood cultures positive for enterococci (odds ratio, 0.14; P = 0.019) and days of antibiotic treatment before FDG-PET/CT (odds ratio, 0.94 per day increase; P = 0.014) were statistically significant independent predictors of a lower odds of detecting an infection focus on FDG-PET/CT. In patients who received antibiotics for less than 7 days before FDG-PET/CT, an infection focus was found in 71% (56/79). In patients who received antibiotics for 8 to 14 days before FDG-PET/CT, an infection focus was found in 52% (22/42). After 15 to 21 days of antibiotic treatment, an infection focus was found in 61% (8/13), and for 22 days or more, this declined to 38% (5/13).

Conclusions FDG-PET/CT is a useful method for detecting an infection focus in patients with BSI. However, longer duration of antibiotic treatment before FDG-PET/CT and bacteremia with enterococci reduce the diagnostic yield of FDG-PET/CT. These factors should be taken into account when considering an FDG-PET/CT scan for this indication.

From the *Medical Imaging Center, Departments of Radiology, Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen

TechMed Centre, Department of Biomedical Photonic Imaging, University of Twente, Enschede; and

Department of Medical Microbiology and Infection Prevention, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.

Received for publication August 14, 2018; revision accepted October 7, 2018.

Conflicts of interest and sources of funding: none declared.

Ethical approval: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.

Informed consent: The local institutional review board approved this retrospective single-center study and waived the requirement for written informed consent (IRB number: 201700145).

Correspondence to: Jordy P. Pijl, BSc, Department of Radiology, Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, Hanzeplein 1, PO Box 30.001 9700 RB, Groningen, The Netherlands. E-mail: j.p.pijl@umcg.nl.

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