Clinical and Treatment-Related Factors Associated with Neutrophil Recovery After Bloodstream Infection in Acute Leukemia: A Competing-Risk Analysis

Background/Objectives: Neutrophil recovery after bloodstream infection (BSI) in acute leukemia is clinically important, but evaluation is complicated by early death and recurrent infectious episodes. We assessed clinical, treatment-related, and microbiological factors associated with recovery while accounting for death as a competing event. Methods: This retrospective single-center cohort included 205 microbiologically documented BSI episodes in 101 adults with acute leukemia treated between 2020 and 2025. Neutrophil recovery was defined as an absolute neutrophil count >500/µL after BSI onset. The endpoint was evaluable in 186 episodes; 116 were followed by recovery and 70 by death before recovery. Recurrent episodes were retained and within-patient dependence was addressed by patient-level clustering in marginal Fine–Gray regression. Results: In the fully adjusted model (177 episodes, 93 patients), G-CSF use was associated with a higher cumulative incidence of recovery (sHR 3.17, 95% CI 1.40–7.18; p = 0.006), as was consolidation versus induction (sHR 2.50, 95% CI 1.44–4.33; p = 0.001). Clinically relevant antimicrobial resistance was not independently associated with recovery (sHR 0.80, 95% CI 0.38–1.68; p = 0.558). A literal-first-BSI sensitivity analysis supported the overall clinical pattern. Conclusions: Neutrophil recovery after BSI was associated primarily with treatment and clinical context, while the crude adverse association with antimicrobial resistance was substantially attenuated after adjustment. These observational associations, particularly those involving G-CSF, should not be interpreted causally.