TF and infection: Participants’ ID were categorized as: the ferritin < 100 ng/mL, transferrin saturation < 20% was defined as “subclinical or functional ID (FID) in Group 1”; ferritin < 30 ng/mL, transferrin saturation < 20%, as “absolute-ID (AID)” in Group 2; ferritin < 12 ng/mL without anemia and infection, as “true ID” in Group 3.