In iron deficiency anemia, which is high: ferritin, MCV (Mean Corpuscular Volume), TIBC (Total Iron Binding Capacity), or transferrin?

Iron Deficiency Anemia Laboratory Parameters

In iron deficiency anemia, Total Iron Binding Capacity (TIBC) is elevated. 1, 2

Laboratory Parameters in Iron Deficiency Anemia

Iron deficiency anemia is characterized by specific changes in laboratory parameters that reflect the body's attempt to compensate for decreased iron stores. These changes include:

• TIBC (Total Iron Binding Capacity): Elevated

  • TIBC measures the blood's capacity to bind iron with transferrin
  • In iron deficiency, TIBC increases as the body attempts to maximize iron transport 1, 2
  • Normal range is typically 250-450 μg/dL, with values often exceeding 350 μg/dL in iron deficiency 3

• Ferritin: Decreased

  • Ferritin is the primary storage form of iron
  • Levels below 30 μg/L indicate depleted iron stores 1
  • Levels below 15 μg/L are highly specific for iron deficiency (specificity 0.99) 1

• MCV (Mean Corpuscular Volume): Decreased

  • Iron deficiency typically causes microcytic anemia (MCV < 80 fL) 1
  • However, MCV may be normal in early iron deficiency or when concurrent conditions exist 1

• Transferrin: Elevated

  • Transferrin is the main iron-transport protein in the blood
  • TIBC essentially measures circulating transferrin 1
  • Transferrin increases in iron deficiency as the body attempts to maximize iron transport 2

Diagnostic Approach

The British Society of Gastroenterology guidelines 1 recommend:

1. Serum ferritin as the most specific test for iron deficiency in the absence of inflammation
2. Transferrin saturation (serum iron divided by TIBC) below 16% reflects impaired iron delivery to erythroid marrow
3. In the presence of inflammation, ferritin may appear normal despite iron deficiency

Clinical Implications

• TIBC measurement outperforms serum iron measurement alone in predicting iron deficiency 4
• A TIBC greater than 70 μmol/L combined with transferrin saturation less than 16% has a 93% predictive value for iron deficiency 5
• In hospitalized patients with transferrin saturation ≤15%, a TIBC ≥350 μg/dL indicates iron deficiency in 54% of cases 3

Common Pitfalls

• Ferritin is an acute phase reactant and may be falsely normal or elevated in inflammatory conditions despite iron deficiency 1
• MCV may be normal in mixed deficiency states (e.g., concurrent B12 or folate deficiency) 1
• Transferrin saturation can be affected by diurnal variation in serum iron levels 1
• Distinguishing between absolute iron deficiency and functional iron deficiency can be challenging in inflammatory states 1

Therefore, among the options presented (ferritin, MCV, TIBC, transferrin), TIBC is the parameter that would be elevated in iron deficiency anemia.