Positive Impact of [18F]FDG-PET/CT on Mortality in Patients With Staphylococcus aureus Bacteremia Explained by Immortal Time Bias

Thomas W. van der Vaart, Jan M. Prins, Cornelis H. van Werkhoven, Thijs ten Doesschate, Robin Soetekouw, Gitte van Twillert, Jan Veenstra, Bjorn L. Herpers, Wouter Rozemeijer, Rogier R. Jansen, Marc J. M. Bonten, Jan T. M. van der Meer

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Abstract

Background: Several studies have suggested that in patients with Staphylococcus aureus bacteremia (SAB) [18F] fluorodeoxyglucose positron emission tomography/computed tomography ([18F]FDG-PET/CT) improves outcome. However, these studies often ignored possible immortal time bias. Methods: Prospective multicenter cohort study in 2 university and 5 non-university hospitals, including all patients with SAB. [18F]FDG-PET/CT was performed on clinical indication as part of usual care. Primary outcome was 90-day all-cause mortality. Effect of [18F]FDG-PET/CT was modeled with a Cox proportional hazards model using [18F]FDG-PET/CT as a time-varying variable and corrected for confounders for mortality (age, Charlson score, positive follow-up cultures, septic shock, and endocarditis). Secondary outcome was 90-day infection-related mortality (assessed by adjudication committee) using the same analysis. In a subgroup-analysis, we determined the effect of [18F]FDG-PET/CT in patients with high risk of metastatic infection. Results: Of 476 patients, 178 (37%) underwent [18F]FDG-PET/CT. Day-90 all-cause mortality was 31% (147 patients), and infection-related mortality was 17% (83 patients). The confounder adjusted hazard ratio (aHR) for all-cause mortality was 0.50 (95% confidence interval [CI]:. 34-.74) in patients that underwent [18F]FDG-PET/CT. Adjustment for immortal time bias changed the aHR to 1.00 (95% CI. 68-1.48). Likewise, after correction for immortal time bias, [18F]FDG-PET/CT had no effect on infection-related mortality (cause specific aHR 1.30 [95% CI. 77-2.21]), on all-cause mortality in patients with high-risk SAB (aHR 1.07 (95% CI. 63-1.83) or on infection-related mortality in high-risk SAB (aHR for 1.24 [95% CI. 67-2.28]). Conclusions: After adjustment for immortal time bias [18F]FDG-PET/CT was not associated with day-90 all-cause or infection-related mortality in patients with SAB.
Original languageEnglish
Pages (from-to)9-15
Number of pages7
JournalClinical Infectious Diseases
Volume77
Issue number1
DOIs
Publication statusPublished - 1 Jul 2023

Keywords

  • Staphylococcus aureus bacteraemia
  • [18F]FDG-PET/CT
  • immortal time bias
  • mortality

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