We found that native serum ferritin protein in COVID-19 patients was composed of approximately 75.4 ± 10.35% FTL and 24.6 ± 10.35% FTH1 (SupplementaryFigure 10B), and that in individuals with ARDS who died had a trend for higher levels of FTL when compared to patients with ARDS who survived (Figure 6M). Here, FTL is linked to acute respiratory distress syndrome.