EDN1 and anemia: To date, biomarkers that have been studied for COVID-19 include hematologic parameters such as anemia (33), platelets (34), ferritin:transferrin ratio (33), peripheral blood leukocyte and lymphocyte counts (35), absolute number of neutrophils (36), monocytes, basophils, eosinophils (37) and eosinophil-derived neurotoxin (EDN-1) levels (38).