Three Distinct Trajectories of Red Blood Cell Distribution Width and Their Significant Association with Mortality in Sepsis Patients: A Group-Based Trajectory Modeling Study with Validation

The red cell distribution width (RDW) is a recognized prognostic marker in sepsis, yet its dynamic changes over time and their relationship with outcomes remain unexplored. This study aimed to identify distinct RDW trajectories during the early phase of sepsis and evaluate their association with mortality. We conducted a retrospective cohort study using data from the MIMIC-IV database (n=3,813) as the derivation cohort and from the First Affiliated Hospital of Kunming Medical University (n=467) for external validation. Sepsis patients with at least seven RDW measurements within the first ten days of hospitalization were included. Group-based trajectory modeling (GBTM) was employed to identify RDW trajectories. A three-trajectory model was selected based on model fit indices and clinical interpretability: Trajectory 1 (Slow-Decrease, 32.97%), Trajectory 2 (Slow-Increase, 43.30%), and Trajectory 3 (Fluctuating-Rapid Decrease, 23.73%). In the our study, Cox models adjusted for confounders revealed that, compared to Trajectory 1, Trajectory 3 was independently associated with significantly increased 30-day (HR 1.47, 95% CI 1.17-1.84) and 90-day mortality (HR 1.54, 95% CI 1.25-1.88). Conversely, Trajectory 2 was associated with the most favorable survival rates. Kaplan-Meier analysis consistently showed the highest mortality in the Trajectory 3 group. External validation confirmed the models robustness and the consistent prognostic value of the identified trajectories. We conclude that dynamic RDW trajectories, readily identifiable from routine clinical data, provide significant prognostic information beyond single-time-point measurements and can aid in the risk stratification of sepsis patients.