Iron deficiency was classified as low or marginal iron stores (ferritin concentrations corrected for inflammation <15 μg/L and <50 μg/L respectively; Fer), iron deficient erythropoiesis (soluble transferrin receptor concentrations >8.3 mg/L; sTfR), or low total body iron (TBI) derived from Fer and sTfR concentrations (<0 mg/kg). The gene discussed is TFRC; the disease is Iron deficiency anemia.