Determinants of diagnostic yield and scan quality of [18F]FDG PET/CT in critically ill patients suspected of infection or inflammation of unknown origin.

Abstract

Background [18F]-fluorodeoxyglucose Positron Emission Tomography combined with Computed Tomography ([18F]FDG PET/CT) is widely used to detect focal inflammation. However, its diagnostic performance and utility in the ICU remain unclear. We aimed to identify factors influencing diagnostic yield and scan quality of [18F]FDG PET/CT in critically ill patients suspected of infection or inflammation. Methods We retrospectively evaluated [18F]FDG PET/CT scans performed in adult ICU patients across four Dutch hospitals (2013–2023). The primary endpoint was diagnostic yield: new conclusive diagnoses and/or therapy changes within 72 h. Secondary endpoints were scan quality and adequacy of myocardial suppression. Logistic regression was used to identify determinants of each endpoint. Results We analyzed 169 scans for 162 clinical indications in 151 patients. A conclusive diagnosis was established for 109 indications (67%), including 79 new diagnoses (49%), most frequently involving the musculoskeletal system (n = 39; 24%) and the respiratory tract (n = 31; 19%). [18F]FDG PET/CT prompted a therapy change in 70 indications (43%). Diabetes (aOR 0.35 [95% CI: 0.15–0.80]) and partial-body imaging versus total-body imaging (aOR 0.48 [CI 0.24–0.99]) were associated with fewer new diagnoses. A longer pre-scan ICU stay predicted therapy change (aOR 1.03 [1.01–1.05]). Higher BMI (aOR 1.08 [1.00–1.17]) and lower serum creatinine (log-transformed aOR 0.36 [0.20–0.68]) were associated with improved scan quality. Male sex (aOR 0.45 [0.21–0.96]) and pre-scan unfractionated heparin (aOR 0.43 [0.19–0.98]) were associated with suboptimal myocardial suppression. Conclusions [18F]FDG PET/CT has a high diagnostic yield in critically ill patients. Diagnostic yield, scan quality and myocardial suppression are influenced by patient characteristics and preparation. Optimizing these factors may further enhance its utility in the ICU.