Serum creatinine-to-albumin ratio as a predictor of 28-day mortality in critically ill patients with ischemic stroke: A retrospective cohort study

The creatinine-to-albumin ratio (CAR) has emerged as a promising prognostic marker in critical illnesses, yet its role in ischemic stroke (IS) remains underexplored. This study aimed to evaluate the association between CAR and 28-day mortality in IS patients admitted to the intensive care unit (ICU). We conducted a retrospective cohort study using data from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. A total of 1,596 IS patients admitted to the ICU between 2008 and 2019 were included. CAR was calculated as the ratio of serum creatinine to albumin levels at ICU admission, and patients were stratified into quartiles based on CAR values. The primary outcome was 28-day all-cause mortality. Multivariate Cox regression models, Kaplan-Meier survival analysis, restricted cubic spline (RCS) analysis, and receiver operating characteristic (ROC) curves were used to assess the predictive value of CAR. Our results showed that higher CAR index was significantly associated with increased 28-day mortality. In multivariate Cox regression analysis, CAR remained an independent predictor of mortality after adjusting for age, gender, race, and comorbidities (HR: 1.33, 95 % CI: 1.12–1.59, p = 0.001). Patients in the highest CAR quartile (Q4) had a 2.76-fold increased risk of mortality compared to those in the lowest quartile (Q1) (HR: 2.76, 95 % CI: 1.93–3.94, p < 0.001). Subgroup analysis revealed that the association was stronger in patients without diabetes or renal disease. RCS analysis demonstrated a non-linear dose–response relationship, with a steeper increase in mortality risk at CAR levels above 0.288. CAR showed moderate predictive performance (AUC: 0.645, 95 % CI: 0.614–0.676), outperforming individual markers such as creatinine and albumin. CAR is an independent predictor of 28-day mortality in IS patients admitted to the ICU. By integrating renal dysfunction and systemic inflammation or malnutrition, CAR provides a comprehensive risk assessment, making it a valuable tool for risk stratification and clinical decision-making.