Can you interpret the CBC results: hemoglobin 113 g/L, hematocrit 0.35 L/L, mean corpuscular volume 90 fL, mean corpuscular hemoglobin 29 pg, red blood cell count 3.91 × 10^12/L?

CBC Interpretation: Mild Normocytic Anemia

These results show mild anemia with normal red blood cell size (normocytic) and normal hemoglobin content per cell (normochromic), requiring further workup to identify the underlying cause.

Analysis of Your Results

Your CBC shows:

• Hemoglobin 113 g/L - Below normal for women (<120 g/L) and men (<130 g/L) 1
• Hematocrit 0.35 L/L (35%) - Slightly low (normal >36% for women, >39% for men) 1
• MCV 90 fL - Normal (normocytic: 80-100 fL) 2
• MCH 29 pg - Normal range
• RBC 3.91 × 10^12/L - Mildly reduced

Classification and Differential Diagnosis

This is a normocytic anemia (MCV 80-100 fL), which has a distinct differential diagnosis compared to microcytic or macrocytic anemias 2.

Most Likely Causes of Normocytic Anemia:

1. Hemorrhage (acute or chronic blood loss)
2. Hemolysis (red blood cell destruction)
3. Anemia of chronic disease/inflammation
4. Bone marrow failure or suppression
5. Renal insufficiency (decreased erythropoietin production)
6. Early iron deficiency (before MCV drops)

Essential Next Steps for Workup

The critical follow-up test is the reticulocyte count 2, 1. This determines whether your bone marrow is responding appropriately to the anemia:

If Reticulocyte Index is LOW (<1.0-2.0):

• Suggests decreased RBC production
• Check: serum ferritin, transferrin saturation, vitamin B12, folate
• Consider: bone marrow dysfunction, chronic kidney disease (check creatinine/GFR)
• Iron deficiency criteria: ferritin <30 μg/L without inflammation, or <100 μg/L with inflammation 3, 1

If Reticulocyte Index is HIGH (>2.0):

• Suggests increased RBC destruction or loss
• Check: haptoglobin, indirect bilirubin, LDH, Coombs test
• Evaluate for: hemolysis or occult bleeding (stool guaiac, endoscopy if indicated) 2

Minimum Required Workup

Based on consensus guidelines 1, you need:

• Reticulocyte count (most important)
• Serum ferritin and transferrin saturation
• CRP (to assess for inflammation)
• Peripheral blood smear review (to confirm RBC morphology)
• Serum creatinine/GFR (to exclude renal insufficiency)
• Vitamin B12 and folate if macrocytic component suspected

Clinical Context Matters

Important considerations:

• In women of reproductive age, menstrual blood loss is a common contributor
• In men and postmenopausal women, gastrointestinal blood loss must be excluded 4
• Symptoms like fatigue, dyspnea, chest pain, or pallor warrant more urgent evaluation 2
• Even mild anemia (hemoglobin <110 g/L) is associated with increased adverse events in certain populations 5

Common Pitfalls to Avoid

• Don't assume normal MCV excludes iron deficiency - early iron deficiency may present with normal MCV before microcytosis develops 1
• Don't overlook combined deficiencies - iron deficiency plus B12/folate deficiency can mask each other, resulting in normal MCV with elevated RDW 2, 1
• Ferritin interpretation requires inflammation assessment - ferritin can be falsely elevated by inflammation, malignancy, or liver disease even when iron deficiency exists 2, 3

Proceed with reticulocyte count and iron studies as the immediate next step to guide further management.