TABLE 1.
Body iron compartments, their respective indicators, and the type of deficiency resulting from the depletion of each compartment
| Iron stores | Transport iron | Functional iron | |
| Commonly used indicators | Stainable bone marrow iron | Transferrin saturation1 (serum iron and either total iron-binding capacity, unsaturated iron-binding capacity, or transferrin) | Hemoglobin (whole blood) |
| Ferritin (serum) | Protoporphyrin2 (erythrocytes) | Hematocrit (whole blood) | |
| Soluble transferrin receptor (serum) | |||
| Deficiency | Iron depletion | Iron deficiency erythropoiesis | Iron deficient anemia |
1
Transferrin saturation is calculated as the ratio of iron to transferrin or iron to total iron-binding capacity; if unsaturated iron-binding capacity is measured, the total iron-binding capacity is calculated as the sum of iron and unsaturated iron-binding capacity.
2
Erythrocyte protoporphyrin can be measured directly as zinc protoporphyrin, the form present in erythrocytes, or as free erythrocyte protoporphyrin after extraction.