What is the initial workup for a 10-month-old with anemia?

Initial Workup for a 10-Month-Old with Anemia

For a 10-month-old infant with anemia, begin with a complete blood count (CBC) with red cell indices (MCV, RDW), reticulocyte count, and serum ferritin to guide diagnosis and treatment. 1, 2, 3

Minimum Laboratory Workup

The essential initial tests include:

• Complete blood count with red cell indices (MCV, RDW, MCH) to classify the anemia as microcytic, normocytic, or macrocytic 1, 4
• Reticulocyte count to assess bone marrow response and distinguish between decreased production versus increased destruction/loss 1, 5
• Serum ferritin to evaluate iron stores (iron deficiency likely if <30 μg/L in absence of inflammation) 1, 2

Additional Initial Tests to Consider

• Transferrin saturation (TfS) to assess functional iron availability 1
• CRP to identify inflammation that may affect ferritin interpretation 1
• Peripheral blood smear for morphologic evaluation 4, 5

Diagnostic Approach Based on MCV

Microcytic Anemia (Most Common at This Age)

Iron deficiency anemia is the most likely diagnosis in a 10-month-old, as this age group (9-18 months) is at highest risk due to rapid growth and frequently inadequate dietary iron intake 1, 6.

If microcytic anemia with risk factors for iron deficiency (exclusive breastfeeding without iron supplementation after 6 months, early cow's milk introduction, >24 oz daily milk intake, low dietary iron), presumptive treatment with oral iron at 3 mg/kg per day between meals is appropriate 1, 2, 3. Confirm diagnosis by repeating hemoglobin in 4 weeks; an increase ≥1 g/dL or hematocrit ≥3% confirms iron deficiency anemia 1, 2, 3.

If severe microcytic anemia or no response to iron therapy, evaluate for:

• Lead level (especially if pica or environmental exposure) 4, 7
• Hemoglobin electrophoresis for thalassemia 4, 7
• Gastrointestinal blood loss 2, 4

Normocytic Anemia

Elevated reticulocyte count suggests hemolysis or blood loss; evaluate with:

• Haptoglobin, lactate dehydrogenase, bilirubin 1
• Direct antiglobulin test (Coombs) 5
• Peripheral smear for hemolysis markers 4, 5

Low/normal reticulocyte count suggests bone marrow suppression or chronic disease; consider:

• Inflammatory markers (CRP, ESR) 1, 5
• Renal function (creatinine, BUN) 1
• Hematology referral if bone marrow disorder suspected 5, 6

Macrocytic Anemia (Uncommon)

Evaluate for:

• Vitamin B12 and folate levels 1, 7
• Thyroid function tests 7, 6

Critical Pitfalls to Avoid

• Do not delay iron supplementation in a 10-month-old with microcytic anemia and clear risk factors while waiting for ferritin results, as this is the peak age for iron deficiency 1
• RDW is particularly useful when MCV is normal but iron deficiency is suspected, as it indicates red cell size variability 1
• Serum ferritin up to 100 μg/L may still indicate iron deficiency in the presence of inflammation, as ferritin is an acute phase reactant 1
• Confirm positive screening with repeat testing before initiating extensive workup 1, 3

When to Refer

Hematology consultation is appropriate if:

• Anemia does not respond to appropriate iron therapy after 4 weeks despite compliance 1, 2
• Cause remains unclear after extended workup 1
• Evidence of bone marrow suppression (low reticulocyte count with normocytic anemia) 5, 6