Utility of 18F-FDG PET/CT for Suspected Infection in the Inpatient Setting: a Single Centre Retrospective Cohort Study

Retrospective cohort study of inpatients at a South Australian tertiary hospital who underwent 18F FDG-PET/CT for investigation of undifferentiated fever or inflammatory syndrome. The aim is to investigate the utility of FDG-PET/CT in the investigation of suspected infection in hospitalised adults. To establish the rate at which FDG-PET/CT contributes to a diagnosis, and how this impacts clinical management and outcomes. From this, to develop further understanding of for which patients this imaging modality contributes meaningfully to outcomes.

Study Overview

• Status: Completed
• Conditions: Inflammation; Fever; Fever of Unknown Origin; Inflammation of Unknown Origin
• Intervention / Treatment: Diagnostic test: 18F-FDG PET/CT

Detailed Description

A retrospective cohort study of consecutive adult inpatients undergoing 18F-FDG PET/CT for suspected infection or inflammation, excluding infective endocarditis and malignancy-directed scans. Pre-PET variables include inflammatory markers, microbiological results, prior imaging findings and infectious diseases (ID) consultation. PET/CT utility will be adjudicated as diagnostic and/or associated with a change in management using a structured consensus process. Associations between pre-PET factors and clinical utility will be explored using descriptive and logistic analyses.

• Study Type: Observational
• Enrollment (Actual): 266

Contacts and Locations

Study Locations

• Australia
  • South Australia
    • Adelaide, South Australia, Australia, 5000
      • Royal Adelaide Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Consecutive adults referred for FDG-PET/CT for evaluation of undifferentiated fever, inflammation or infection.

Description

Inclusion Criteria:

• Inpatient at the Royal Adelaide Hospital
• FDG-PET/CT between 1st January 2022 - 31st December 2023
• Imaging request query included: infect* AND/OR Fever of Unknown Origin OR FUO AND/OR Pyrexia of Unknown Origin OR PUO AND/OR inflammat*

Exclusion Criteria:

• - Outpatient PET/CT
• Comparison imaging for established diagnosed infection
• PET/CT intended for evaluation of malignancy
• Evaluation of presumed or confirmed infective endocarditis
• Age less than 18 years

Study Plan

How is the study designed?

Number of groups / cohorts

8

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Infectious diseases consultation	Diagnostic test: 18F-FDG PET/CT; Nuclear medicine imaging as a diagnostic tool with implication for change in clinical management
No infectious diseases consultation	Diagnostic test: 18F-FDG PET/CT; Nuclear medicine imaging as a diagnostic tool with implication for change in clinical management
Significant pre-PET imaging finding	Diagnostic test: 18F-FDG PET/CT; Nuclear medicine imaging as a diagnostic tool with implication for change in clinical management
No significant pre-PET imaging finding	Diagnostic test: 18F-FDG PET/CT; Nuclear medicine imaging as a diagnostic tool with implication for change in clinical management
High blood WCC prior to PET	Diagnostic test: 18F-FDG PET/CT; Nuclear medicine imaging as a diagnostic tool with implication for change in clinical management
Low WCC prior to PET	Diagnostic test: 18F-FDG PET/CT; Nuclear medicine imaging as a diagnostic tool with implication for change in clinical management
High CRP prior to PET	Diagnostic test: 18F-FDG PET/CT; Nuclear medicine imaging as a diagnostic tool with implication for change in clinical management
Low CRP prior to PET	Diagnostic test: 18F-FDG PET/CT; Nuclear medicine imaging as a diagnostic tool with implication for change in clinical management

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Diagnostic yield	• Did PET contribute to diagnostic yield?: 1 = Yes: PET led to a finding either definitive e.g. confirmed by gold standard (microbiology, histopathology, intraoperative findings etc) or contributory, which guided diagnosis or management even without gold standard confirmation. Examples of contributory: PET showing vascular graft uptake, not explanted due to risk but presumptively treated Vertebral discitis suggested by PET, biopsied without culture, but presumptively treated and clinically improved PET negative - antibiotics ceased, patient remained well; 0 = No: PET provided no new information, was misleading (i.e. PET result contradicted by later results), or no action was taken based on PET	30 days

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Clinical change in management	• Clinical change in management: was clinical care altered compared to the documented plan prior to PET? 0 = no, 1 = yes; Yes: antimicrobial therapy, procedures/interventions (PET-guided site biopsy, or surgery/drainage), diagnostics e.g. further focussed imaging, or disposition e.g. palliative care transition; No: there was no change to the management plan, or the plan was already determined by other data Examples: PET confirmed a suspected diagnosis but the treatment plan was unchanged; PET provided supporting evidence but no explicit management adjustment was documented; PET was negative and no further management steps were taken because there was a pre-existing plan	30 days
Change in antimicrobial management	•Change in antimicrobial duration/spectrum/therapeutic procedure: this change occurred as a result of PET	30 days
Final diagnosis	• Final diagnosis: infection = 1, non-infectious = 2, malignancy = 3, unresolved = 4	30 days

Collaborators and Investigators

• Sponsor: University of Adelaide
• Collaborators: Central Adelaide Local Health Network Incorporated

Study record dates

Study Major Dates

• Study Start (Actual): January 4, 2022
• Primary Completion (Actual): January 29, 2024
• Study Completion (Actual): January 29, 2024

Study Registration Dates

• First Submitted: February 18, 2026
• First Submitted That Met QC Criteria: February 18, 2026
• First Posted (Actual): February 24, 2026

Study Record Updates

• Last Update Posted (Actual): February 24, 2026
• Last Update Submitted That Met QC Criteria: February 18, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: PET; FDG-PET/CT; fever of unknown origin
• Additional Relevant MeSH Terms: Pathologic Processes; Body Temperature Changes; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Inflammation; Fever; Fever of Unknown Origin
• Other Study ID Numbers: 20340

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No