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

## TL;DR

Tracking white blood cell levels over time in sepsis patients can better predict outcomes like death and kidney injury compared to single measurements.

## Contribution

This study shows that longitudinal white blood cell trajectory patterns improve risk prediction for sepsis patients.

## Key findings

- Four distinct WBC trajectory groups were identified with varying mortality risks.
- High WBC trajectories were linked to higher mortality and secondary AKI.
- Low WBC trajectories showed significantly reduced mortality risk.

## Abstract

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.

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.

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.

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).

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.