Laboratory Tests for Iron Stores and Iron Availability

Iron; needed for life, but potentially very toxic (free radicals).

Tests of iron metabolism
Serum iron ( SI)
 * F: 600-1400 mg/L, 11-25mmol/L
 * M: 750-1500 mg/L, 13-27mmol/L
 * Low in Fe deficiency and chronic disease
 * High in hemolytic syndromes and iron overload

Total iron binding capacity (TIBC)
 * amount of iron needed to bind to all the transferrin
 * 2500 – 4500 mg/L, 45-82 mmol/L
 * High in Fe deficiency
 * Low in chronic disease

Serum ferritin
 * Fe storage glycoprotein
 * Can store up to 2000 Fe
 * 30-300 ng/mL)
 * Serum level is very low, but closely correlates with level in cells
 * Closely correlates with total body Fe stores
 * <12 ng/mL Fe deficiency
 * Elevated in Fe overload, liver injury, tumors (Acute phase protein)
 * Tests for iron metabolism

Additional;

Serum transferin receptor Increase in increased erythropoiesis and early Fe deficiency

RBC ferritin

storage status over the previous 3 month (Fe deficiency/overload) unaffected by liver function or acute illness

Free RBC porphyrin

increased when heme synthesis altered

Iron Deficiency Anemia
Prelatent; (Decreasing iron stores of organism)
 * Decrease in serum ferritin – most sensitive parameter
 * decrease of iron in BM – (iron is in BM cells in form of ferritin)
 * increase TIBC (body has tendency to increase the absorption of iron and iron transporting capacity)this leads to decrease in Tf saturation even when serum iron is normal

Latent; (Decreases serum iron available for erythropoiesis)
 * decrease serum iron
 * further decrease Tf saturation
 * increase sTfR

Manifest anemia
 * parameters of anemia (low Hb, Hct, Erythrocyte count)
 * anemia of iron deficiency is hypochromic and microcytic