What labs should be ordered for a patient with iron deficiency anemia?

Additional Laboratory Tests for Iron Deficiency Anemia Workup

For a 39-year-old female with lab values showing hemoglobin 11.3 g/dL, platelets 125, and ferritin 25.5 μg/L, additional testing should include transferrin saturation, total iron binding capacity (TIBC), serum iron, and celiac disease screening with tissue transglutaminase antibodies. 1

Current Lab Interpretation

The patient's current labs suggest iron deficiency anemia:

• Hemoglobin 11.3 g/dL (below normal for women)
• Low RBC count (3.7)
• Low platelet count (125)
• Low ferritin (25.5 μg/L) - while not severely low, it's in the concerning range

Recommended Additional Laboratory Tests

1. Iron Studies:

   • Serum iron
   • Total iron binding capacity (TIBC)
   • Transferrin saturation (iron/TIBC × 100) 2, 1

2. Celiac Disease Screening:

   • Tissue transglutaminase (tTG) antibody test 1
   • This is crucial as 2-5% of patients with iron deficiency anemia have celiac disease 2, 1

3. Complete Blood Count Parameters:

   • Reticulocyte count and reticulocyte hemoglobin content (CHr)
   • Red cell distribution width (RDW) 1, 3

Rationale for Testing

• Transferrin saturation: A value <20% strongly suggests iron deficiency, and <30% helps confirm diagnosis in borderline cases 1

• Celiac disease screening: Essential in all iron deficiency cases as it's found in 3-5% of iron deficiency anemia patients 1

• Reticulocyte hemoglobin content (CHr): Provides an early indication of iron availability and iron-deficient erythropoiesis; useful for monitoring treatment response 3, 4

• RDW: Elevated RDW (>14%) with low MCV is characteristic of iron deficiency 1

Clinical Considerations

• The patient's ferritin level (25.5 μg/L) is borderline low. While a level <15 μg/L is highly specific for iron deficiency, levels <30 μg/L are still concerning 1, 5

• The low platelet count (125) may be related to iron deficiency or could indicate another underlying condition that requires investigation

• The patient's TSH (1.69) is normal, ruling out thyroid disease as a cause of anemia

Important Caveats

• Ferritin can be falsely elevated in inflammatory conditions, masking true iron deficiency 1

• Relying solely on hemoglobin and hematocrit without measuring iron status indicators can miss iron depletion 6

• IgA deficiency can cause false-negative tTG results when screening for celiac disease 1

• If initial testing confirms iron deficiency anemia, gastrointestinal evaluation should be considered to rule out occult bleeding sources 2

By obtaining these additional tests, you'll be able to confirm the diagnosis of iron deficiency anemia, screen for common underlying causes like celiac disease, and establish baseline values for monitoring treatment response.