What labs are used to check for iron deficiency or overload?

Laboratory Tests for Iron Status Assessment

A complete iron panel should include serum ferritin, transferrin saturation (TSAT), serum iron, total iron binding capacity (TIBC), complete blood count with reticulocytes, and hemoglobin to properly assess iron deficiency or overload. 1

Core Iron Panel Components

• Serum Ferritin: Reflects total body iron stores; primary marker for iron deficiency and overload 1

  • Values <12 ng/mL indicate absolute iron deficiency in general population 1
  • Values <100 ng/mL suggest iron deficiency in chronic kidney disease patients 1
  • Values >1,000 μg/L may indicate iron overload and warrant consideration for liver biopsy 1

• Transferrin Saturation (TSAT): Calculated as (serum iron × 100)/TIBC; reflects iron immediately available for hemoglobin synthesis 1

  • Values <20% suggest iron deficiency 1
  • Values >45% suggest potential iron overload 1

• Serum Iron: Measures circulating iron bound to transferrin 1

  • Subject to diurnal variation; best collected at consistent times 1

• Total Iron Binding Capacity (TIBC): Measures transferrin's capacity to bind iron 1

  • Elevated in iron deficiency 1
  • Decreased in iron overload and inflammation 1

• Complete Blood Count (CBC): Evaluates red blood cell parameters 1

  • Hemoglobin and hematocrit are late indicators of iron deficiency 1
  • Mean cell volume (MCV) - microcytosis may indicate iron deficiency 1
  • Red cell distribution width (RDW) - increased in iron deficiency 1

Additional Tests for Specific Scenarios

• Reticulocyte Hemoglobin Content: Early marker of functional iron deficiency; not widely available in the US 1, 2

• Percentage of Hypochromic Red Blood Cells: Values >10% suggest iron deficiency in patients on erythropoietin therapy 1

  • Requires specialized equipment (Technicon H-1, H-2, H-3 Autoanalyzers) 1

• MRI for Liver Iron Content: Gold standard for non-invasive assessment of iron overload 1

  • Validated R2, T2*, or R2* methods should be used 1
  • Same method should be used over time for consistency 1

• Cardiac T2 MRI*: For assessment of cardiac iron overload in severe cases 1

  • Particularly important in juvenile hemochromatosis 1

Interpretation Challenges

• Inflammation Effect: Ferritin is an acute phase reactant; levels increase during inflammation, potentially masking iron deficiency 1, 3

• Functional Iron Deficiency: May occur despite normal ferritin when iron mobilization is impaired 1, 2

  • Common in patients receiving erythropoietin therapy 1

• Discordant Results: When ferritin and TSAT give conflicting information 1, 2

  • High ferritin with low TSAT may indicate inflammatory iron block 1
  • Complete iron profile rather than ferritin alone should be used 3

Special Considerations

• Chronic Kidney Disease: Higher ferritin thresholds for iron deficiency (typically <100 ng/mL) 1

  • IV iron may be beneficial even with ferritin 100-700 ng/mL if TSAT <20% 1

• Athletes: Higher risk of iron deficiency, especially female athletes, endurance athletes, and those with restrictive diets 1

  • Consider screening in high-risk athletic populations 1

• Obesity: Ferritin may be elevated due to inflammation rather than adequate iron stores 3

  • Complete iron profile including transferrin is more reliable than ferritin alone 3

• Hemochromatosis Screening: Requires both TSAT and ferritin 1, 4

  • TSAT >45% and ferritin >200 μg/L (female) or >300 μg/L (male) warrant further evaluation 1

Remember that no single test is definitive for iron status assessment, and results must be interpreted in clinical context 1.