The Relationship Between CRP/Albumin Ratio and In-Hospital Mortality in Intensive Care Patients: A Retrospective Observational Study

Introduction: Accurate prognostic assessment in intensive care units (ICUs) is crucial for early risk stratification and efficient resource allocation. The C-reactive protein to albumin ratio (CAR) has recently gained attention as a composite biomarker that reflects both systemic inflammation and nutritional status. The present study sought to determine whether CAR measured at ICU admission could predict in-hospital mortality among critically ill adults and to establish its optimal discriminatory threshold. Methods: This single-center retrospective cohort study included 1,846 adult patients (aged ≥18 years) who were admitted to the ICU between January 2023 and June 2025. At the point of admission, demographic, clinical, comorbidity, and laboratory data were thoroughly recorded. Mortality predictors were evaluated via logistic regression methods. The capacity of CAR for discrimination was determined using receiver operating characteristic analysis. Results: Overall in-hospital mortality was 24.2% (n=446). Non-survivors were significantly older, with lower body weight and body mass index, and with higher rates of diabetes, chronic kidney disease, malignancy, heart failure, sepsis, infection, and acute kidney injury (AKI). The CAR at admission was markedly higher in non-survivors (5.5±5.3 vs. 1.5±2.6, p<0.001). In multivariable logistic analysis, independent factors associated with in-hospital mortality included age, polypharmacy, heart failure, infection, AKI, and CAR. The best threshold identified for CAR was 1.715, providing 76.9% sensitivity and 73.6% specificity, while its negative predictive value reached 90.9%. Conclusion: Admission-time CAR measurement proved to be an effective indicator of in-hospital mortality among ICU patients. Its simplicity and cost-effectiveness underscore its utility as a prognostic instrument for early risk stratification in critical care.