The role of Frailty Index Laboratory in predicting clinical outcomes in patients with Clostridioides difficile infections: a 2020–24 single-centre retrospective study

Background: Clostridioides difficile infection (CDI) is considered one of the most significant healthcare-asso- ciated infections with significant morbidity and mortality. Frailty, characterized by diminished physiological re- serves, has emerged as a critical determinant of poor outcomes. The Frailty Index based on Laboratory tests (FI- Lab), derived from routine laboratory parameters, offers an objective tool for assessing frailty. The primary aim of this study was to assess the efficacy of FI-Lab in predicting mortality and recurrence in CDI hospitalized patients. Methods: This retrospective study analysed data from 280 patients diagnosed with CDI, hospitalized at the Policlinic of Bari between 2020 and 2024. Frailty was assessed using FI-Lab, based on 35 routine laboratory tests. Primary outcomes included 14- and 28-day mortality, recurrence during hospitalization and recurrence post- discharge. Associations between FI-Lab and outcomes were evaluated. Results: Of the 280 patients included, 213 survived and 67 died during hospitalization or within 28 days post- infection. Non-survivors had significantly higher FI-Lab scores compared to survivors (0.70±0.15 versus 0.25 ± 0.12, P < 0.0001). FI-Lab demonstrated excellent discrimination for mortality at 14 and 28 days, with each 0.10-point increase in FI-Lab associated with elevated mortality risk. Predictive accuracy for recurrence was moderate (AUC = 0.73 for recurrence within 60 days post-discharge). Fidaxomicin use did not significantly re- duce mortality or recurrence after adjustment for FI-Lab and comorbidities. Conclusions: FI-Lab is a predictor of mortality in CDI patients and a valuable tool for early risk stratification. Its utility in predicting recurrences is limited. Prospective studies are warranted to validate these findings and refine therapeutic approaches for high-risk patients.