Prognostic Nutritional Index Predicts In-Hospital Mortality Among Patients with Clostridioides difficile Infection: A Real-World Retrospective Study

Background/Objectives: Clostridioides difficile infection (CDI) remains a major cause of morbidity and mortality, particularly among hospitalized older adults. This study evaluated the prognostic performance of routinely available inflammatory and nutritional biomarkers for predicting in-hospital mortality in patients with CDI. Methods: We conducted a retrospective observational study of 110 adults with confirmed CDI admitted to the Internal Medicine Department of a tertiary-care hospital in Athens, Greece, between January 2022 and December 2025. Demographic, clinical, and laboratory data obtained within 24 h of admission were analyzed. The prognostic value of the neutrophil-to-lymphocyte ratio (NLR), derived neutrophil-to-lymphocyte ratio (dNLR), C-reactive protein-to-albumin ratio (CAR), and Prognostic Nutritional Index (PNI) was assessed using univariate and multivariate logistic regression analyses. Receiver operating characteristic (ROC) curve analysis evaluated the discriminatory performance of PNI. Results: Twenty-two patients (20.0%) died during hospitalization. Compared with survivors, non-survivors exhibited significantly higher NLR (p = 0.035), dNLR (p = 0.012), and CAR (p = 0.015) values, whereas serum albumin and PNI were significantly lower (both p < 0.001). In univariate analysis, dNLR, CAR, and PNI were associated with mortality. After adjustment for age, sex, length of stay, and cancer diagnosis, only PNI remained independently associated with in-hospital mortality (p = 0.018). PNI showed good predictive performance (p < 0.001). Conclusions: PNI is a simple, inexpensive, and readily obtainable biomarker independently associated with in-hospital mortality in CDI. These findings highlight the importance of immune-nutritional status in CDI and support the potential utility of PNI for early risk stratification in hospitalized patients.