Early Serum Ferritin (Days 5–8) is a Robust Prognostic Marker for Severe Illness and Mortality in Hospitalized COVID-19 Patients: A Retrospective Observational Study

Background COVID-19 induces immune dysfunction and excessive inflammation, marked by rising acute phase reactants like ferritin. While elevated ferritin indicates severe illness, timing and specific thresholds for predicting critical outcomes and mortality requires further clarification. Methods A retrospective observational review occurred at a Karnataka-based teaching hospital in secondary care. The study included patients with confirmed COVID-19 diagnoses using RT-PCR testing who received admission between April 2020 and March 2021 when they fulfilled criteria of hospital stay longer than 7 days combined with their availability for Day 5–8 ferritin tests. A Receiver Operative Characteristic (ROC) curve analysis assessed the relation between ferritin levels and critical illness and mortality outcomes among the severity groups. Results The research included 470 patients. The ferritin concentrations of severe patients reached 886.21 ± 358.11 ng/mL which yielded statistically significant results compared to non-severe patients at 310.11 ± 200.95 ng/mL (p < 0.001). The analysis showed here that elevated ferritin levels measured between Days 5–8 were highly predictive of critical illness (AUC: 0.878 , 95% CI: 0.83–0.92) and mortality (AUC: 0.894 , 95% CI: 0.85–0.94). Patients with ferritin levels exceeding 1000 ng/mL faced greater danger of becoming critically ill as well as dying from COVID-19. Conclusion Evidence reveals that high serum ferritin concentrations measured between Days 5–8 of COVID-19 infection are powerfully linked to serious disease pathophysiology, intensive care requirements and fatality rates especially when it exceeds 1000 ng/ml. A ferritin test provides valuable information which could guide clinicians in choosing early targeted interventions and advanced supportive care.