Exploratory Evaluation of Potential CRP and Ferritin Thresholds and Survival in Critically Ill Patients: A Pilot Prospective ICU Study

Introduction: Iron deficiency is a common condition in the general population, with a higher incidence in critically ill patients. Anemia associated with these alterations is linked to increased morbidity and mortality in ICU patients. Objective: This pilot study explored whether provisional CRP and ferritin thresholds might relate to survival and examined preliminary associations with analytical and clinical variables in critically ill patients. Material and Method: A prospective, observational pilot study was conducted on 75 ICU patients over three months. Hematological and biochemical parameters (CRP, ferritin, iron, transferrin, hemoglobin) were analyzed at admission, 48 hours, and on days 4 and 7. Clinical data included age, sex, ICU stay, survival, SOFA and APACHE II scores, complications (AKI, acute lung injury), and interventions (mechanical ventilation, in-fections). Data were analyzed using mixed regression models and Wilcoxon tests. Results: In this pilot cohort (mean age 53.65 years; 61.33% male), survival was 82.67%. Higher CRP and ferritin levels were observed among non-survivors and those with AKI p< 0.05. A CRP level ≥145 mg/L was associated with a constellation of more unfavorable clinical indicators (older age, longer ICU stay, higher APACHE II and SOFA scores, more me-chanical ventilation, higher AKI and infection rates, and reduced survival) p< 0.05. Ferritin levels were higher in males and non-survivors and showed positive correlations with SOFA score and ICU length of stay. The exploratory prognostic performance of the CRP threshold was AUC=0.8103