Retrospective analysis showed that serum creatinine trajectories are important predictors of 28-day mortality in patients with acute kidney injury superimposed on chronic kidney disease. Using group-based trajectory modelling, five distinct serum creatinine trajectory patterns were identified. Moderate stable, moderate high stable, and high decreasing trajectories were associated with a higher risk of short term mortality, with each pattern reflecting different patient characteristics and comorbidity profiles.This study evaluated the relationship between short-term longitudinal serum creatinine trajectories and 28-day mortality in patients with acute kidney injury and chronic kidney disease. Data were obtained from the Medical Information Mart for Intensive Care database. Group-based trajectory modelling was used to classify serum creatinine patterns during the first 96 hours after admission to the intensive care unit. Survival probabilities over twenty-eight days were compared across different trajectory groups. Multivariable regression models were used to examine the association between serum creatinine trajectories and short-term mortality. The predictive performance and clinical usefulness of the mortality prediction model were also evaluated. Subgroup analyses were performed to evaluate the consistency of the findings. The study included patients with acute kidney injury due to chronic kidney disease who were categorised into five distinct serum creatinine trajectory groups. These included a low stable group, a high decreasing group, a moderate low stable group, a moderate stable group, and a moderate high stable group. Patients in the low stable, high decreasing, and moderate low stable groups had higher short term survival compared with those in the moderate stable and moderate high stable groups. Compared with the low stable group, patients with high decreasing, moderate stable, and moderate high stable serum creatinine trajectories had an increased risk of death within twenty-eight days. The predictive model demonstrated good performance and meaningful clinical benefit across a wide range of risk thresholds. The association between moderate stable and moderate high stable serum creatinine trajectories and increased short term mortality was observed in both male and female subgroups.Overall, patients with acute kidney injury on chronic kidney disease who exhibited high decreasing, moderate stable, or moderate high stable serum creatinine trajectories had a higher risk of twenty-eight-day mortality.Reference:Ying, J., Zhou, H., Zhang, Y. et al. Association of different serum creatinine trajectories with 28 day mortality in patients with acute kidney injury on chronic kidney disease based on the Medical Information Mart for Intensive Care database. European Journal of Medical Research (2025).Keywords:Serum creatinine, twenty eight day mortality, trajectory analysis, chronic kidney disease, acute kidney injury, Ying, J., Zhou, H., Zhang, Y