Description
Patient Preparation: Patient should be drawn fasting in the morning (circadian rhythm affects Fe). Have sample drawn before patient is given therapeutic iron or blood transfusion
Use: Differential diagnosis of anemia, especially with hypochromia and/or low MCV. The percent saturation sometimes is more helpful than is the iron result for iron deficiency anemia. Evaluate thalassemia and possible sideroblastic anemia; work-up hemochromatosis, in which iron is increased and iron saturation is high. Decrease in iron level after performance of Schilling supports the diagnosis of vitamin B12 deficiency, vide infra. Evaluate iron poisoning (toxicity) and overload in renal dialysis patients, or patients with transfusion dependent anemias. Use of TIBC in iron toxicity may be less useful than previous believed.1 TIBC or transferrin is a useful index of nutritional status.
Limitations: Ferritin levels are also useful for iron deficiency. Low iron level may not indicate iron deficiency in acute infection with leukocytosis. Low iron levels may be misleading in chronic infection, inflammation and malignancy; high ferritin levels occur in many such states, however, the most sensitive test for iron deficiency is bone marrow examination. TIBC and transferrin are increased in patients on oral contraceptives, with normal saturation. Gross hemolysis may interfere with serum iron.