Ferritin at admission as a prognostic marker in older adults hospitalized for COVID-19: A retrospective cohort study

• The severity of the disease affected the link between ferritin and mortality. • Ferritin might help guide treatment choices for older people with severe COVID-19. • Ferritin does not strongly predict mortality in older people with COVID-19. • Older people with non-severe COVID-19 benefit from shorter hospital stays. Background: Older adults remain vulnerable to COVID-19 waves, particularly in low-income countries with health disparities, so the discovery and validation of accessible clinical tools are required. Despite the expected changes associated with aging, little has been studied on ferritinemia as a prognostic marker, specifically in this population. Objective: Evaluate the use of serum ferritin levels at hospital admission as a prognostic marker in older adults hospitalized for COVID-19. Material and methods: This monocentric study included people over 60 hospitalized for COVID-19 between 2021 and 2022. Disease presence was assessed with polymerase chain reaction and ferritin with spectrophotometry. Multiple logistic regression models, as well as ROC and Kaplan-Meier curves, were used. Results: In 239 older adults, the association between serum ferritin and mortality was modified by the presence of clinical severity data at admission, being a poor prognosis factor only for those with severe COVID-19 (OR=2.82, p = 0.028, controlling for age and immunization doses). The best cut-off point was 355 ng/dl (Sensitivity: 88.3 %; Specificity: 27.4 %). However, there were no differences in survival curves. Conclusions: Serum ferritin levels could help guide therapeutic decisions in older adults with severe COVID-19 but do not predict mortality independently.