Ferritin Levels in Patients with Acute Bronchiolitis in the Pre-COVID-19 Era

Background: Serum ferritin levels, biomarkers that seem to be associated with disease severity in adults with coronavirus disease 2019 (COVID-19) infection, are unknown in acute bronchiolitis (AB). Our objective is to explore the serum ferritin levels in a sample of infants with AB and to see if they are correlated with severity.Methods: This was a secondary analysis of an ongoing single-centre prospective cohort study including infants aged < 12 months-old with AB between 2018 and 2019. All patients underwent clinical, laboratory, and microbiologic evaluations. The blood collection was drawn, and an aliquot was frozen at -80ºC, within the first 24 hours after admission. For this work, those samples have been thawed, and a ferritin analysis has been performed. Biochemical data were recorded. The primary outcome was to determine the value of serum ferritin in patients with AB according to the severity groups.Findings: We analysed 102 congealed samples of patients with AB. The median age was 1 (0-2) month, and there were 62 (59%) males in the sample. A total of 16 (15.2%) cases presented with a known comorbidity associated with the development of a severe disease. The median value of serum ferritin was 236 ng/ml (IQR: 131-367). There was no statistical difference between the median value of serum ferritin in the severe group (26 patients) and non-severe group (76 patients) (274 ng/ml (IQR: 185-469) vs 230 ng/ml (IQR: 102-340), p= 0.495).Interpretation: Ferritin levels are not associated with disease severity in AB. Although they are not useful as biomarkers for severity in AB, the absence of elevated ferritin levels observed in our cohort suggest a potential role to differentiate severe bronchiolitis from other severe respiratory diseases, such as COVID-19.Funding: The work has not been funded by any source.Declaration of Interest: None of the authors in this manuscript has any conflict of interest to declare.Ethical Approval: The study was approved by the Institutional Review Board of the local ethical investigation committee. Written informed consent was obtained.