# Diagnostic Utility of Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in Infectious Diseases: A Retrospective Study

## TL;DR

This study examines how useful PET/CT scans are for diagnosing infectious diseases, finding they are most helpful for focal infections but less so for unexplained fevers.

## Contribution

The study provides insights into the diagnostic value of PET/CT for specific infectious disease indications based on real-world patient data.

## Key findings

- PET/CT confirmed diagnoses in 60.7% of cases and showed usefulness in 76.4%.
- Focal infections had higher diagnostic confirmation rates compared to fever of unknown origin.
- Only 9.5% of patients without an initial diagnosis received a later confirmation.

## Abstract

Aim: This study aims to evaluate the utility of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) test for various infectious indications, analyze its diagnostic value, and assess its correlation with suspected diagnoses. Additionally, secondary endpoints include evaluating the test's usefulness in clinical management and identifying predictors of PET/CT positivity.

Methods: A retrospective descriptive observational study was conducted on in-hospital patients who underwent 18F-FDG PET/CT for suspected infections.

Results: A total of 89 patients were reviewed. The predominant symptoms were fever (68.5%) and respiratory symptoms (38.2%). The most common prior complementary tests were microbiological (89.9%) and imaging (94.4%). Indications for PET/CT included fever of unknown origin (27%), focal infections (20.2%), bacteremia (34.8%), and immunocompromised patients (18%). Diagnostic confirmation was achieved in 60.7% of cases. The test's usefulness (confirmation and unexpected findings) was 76.4%. Only 9.5% of patients without an initial diagnosis after PET/CT received a confirmatory diagnosis later. The subgroup analysis revealed that fever of unknown origin was associated with a lower probability of confirmation and usefulness, whereas focal infection was linked to a higher likelihood of diagnostic confirmation. However, these associations did not persist in multivariate analysis due to the limited sample size.

Conclusion: Our study aims to optimize the diagnostic profitability of the 18F-FDG PET/CT test for specific infectious disease indications by analyzing previous literature. In our experience, the PET/CT test demonstrated a high percentage of diagnostic confirmation for patients with focal infections. In contrast, its diagnostic yield was significantly lower for prolonged fever of unknown origin.