The Impact of White Blood Cell Count Trajectories on Prognosis and Secondary Acute Kidney Injury in Sepsis Patients.

BACKGROUND

Sepsis-associated acute kidney injury (SA-AKI) is a common and severe complication in critically ill patients, yet the prognostic value of longitudinal white blood cell (WBC) dynamics remains underexplored. Most studies rely on single-timepoint measurements, potentially overlooking important dynamic information for risk stratification.

OBJECTIVES

This study aimed to identify distinct WBC trajectory patterns during the first 7 days of ICU admission and evaluate their associations with mortality and secondary AKI in sepsis patients.

METHODS

This retrospective cohort study analyzed 15,328 adult sepsis patients from the MIMIC-IV database (version 3.1) between 2008 and 2019. Group-based trajectory modeling (GBTM) was applied to daily WBC counts to identify trajectory subgroups. The primary outcome was 28-day mortality, with secondary outcomes including 90-day mortality and secondary AKI occurring after day 7. Cox proportional hazards regression was used to estimate hazard ratios with 95% confidence intervals. Subgroup analyses evaluated effect consistency across clinically relevant characteristics.

RESULTS

Four distinct WBC trajectory groups were identified: high (n = 812, 5.3%), medium-high (n = 2,830, 18.5%), medium-low (n = 7,121, 46.5%), and low (n = 4,565, 29.8%), with overall mean WBC counts of 24.13, 16.60, 11.24, and 6.64 × 109/L, respectively. The 28-day mortality rates were 31.2%, 20.7%, 14.8%, and 12.9% for high, medium-high, medium-low, and low groups, respectively (log-rank p  < 0.001). Compared with the high group, the low trajectory demonstrated significantly reduced mortality risk (HR: 0.36, 95% CI: 0.31-0.42, p  < 0.001). The high-trajectory group exhibited higher secondary AKI incidence (21.8% vs. 13.0%, p  < 0.001) and greater disease severity. A significant interaction was observed for AKI status (P for interaction = 0.003).

CONCLUSIONS

Longitudinal WBC trajectory patterns provide superior prognostic information compared to single-timepoint measurements in sepsis patients, with persistently high WBC levels associated with increased mortality and secondary AKI risk.