What is the interpretation of a lab result showing anemia?

Laboratory Interpretation: Normocytic Anemia

This patient has normocytic anemia (low hemoglobin, hematocrit, and RBC count with normal MCV) that requires iron studies and further evaluation to determine the underlying cause, as normocytic anemia can result from chronic disease, early iron deficiency, hemolysis, or bone marrow dysfunction. 1

Key Laboratory Findings

• Hemoglobin 11.1 g/dL (reference 13.2-17.1): Confirms anemia, falling below the lower limit of normal for this laboratory 1
• Hematocrit 34.4% (reference 38.5-50.0): Proportionally decreased, consistent with anemia 1
• RBC count 3.88 million/uL (reference 4.20-5.80): Low, indicating decreased red blood cell mass 2
• MCV 88.7 fL (reference 80.0-100.0): Normal—this is normocytic anemia, NOT microcytic 1
• MCH 28.6 pg and MCHC 32.3: Both normal, indicating normochromic red cells 1

Classification and Significance

This is normocytic, normochromic anemia. The normal MCV distinguishes this from iron deficiency anemia (which typically presents with microcytosis and hypochromia as late findings) and from macrocytic anemias due to B12/folate deficiency 1. However, MCV can remain normal in early iron deficiency before microcytosis develops 1.

Essential Next Steps for Diagnosis

Immediate Laboratory Evaluation Required:

1. Iron studies (mandatory): 1

   • Serum ferritin (most useful single marker for iron stores)
   • Transferrin saturation (TSAT)
   • Serum iron and total iron-binding capacity
   • Ferritin <25 ng/mL in males or <11 ng/mL in females suggests iron deficiency 1

2. Complete blood count with differential: 1

   • White blood cell count and platelets to assess for bone marrow dysfunction
   • Abnormalities in two or more cell lines warrant hematology consultation 1

3. Reticulocyte count: 1

   • Low reticulocyte count suggests inadequate bone marrow response (chronic disease, erythropoietin deficiency, inflammation)
   • Elevated count suggests hemolysis or acute blood loss with appropriate marrow response

4. Peripheral blood smear: 2

   • Evaluates red cell morphology
   • Can identify hemolysis, hemoglobinopathies, or other structural abnormalities

Additional Considerations:

• Vitamin B12 and folate levels if macrocytic indices develop or if dietary deficiency suspected 1
• Inflammatory markers (CRP, ESR) if chronic disease suspected, as ferritin is an acute-phase reactant and can be falsely elevated with inflammation 1
• Renal function (creatinine, eGFR) to assess for chronic kidney disease, which causes normocytic anemia through erythropoietin deficiency 1

Common Causes of Normocytic Anemia

1. Anemia of chronic disease/inflammation: Most common in adults, often normocytic and normochromic 1
2. Early iron deficiency: Before microcytosis develops 1
3. Chronic kidney disease: Erythropoietin deficiency causes normocytic anemia 1
4. Hemolysis: Elevated reticulocyte count would be present 2
5. Bone marrow disorders: Aplastic anemia, myelodysplasia, or infiltrative processes 1
6. Acute blood loss: With appropriate reticulocyte response 2

Critical Pitfalls to Avoid

• Do not assume normal MCV excludes iron deficiency—iron studies are essential as MCV is a late marker of iron deficiency 1
• Do not rely on hemoglobin/hematocrit alone without iron studies, as this misses early iron depletion 3
• Ferritin can be falsely normal or elevated in the presence of inflammation, infection, or chronic disease despite true iron deficiency 1
• Hemoglobin and hematocrit are late indicators of iron deficiency and only fall after iron stores are depleted 1
• In men and postmenopausal women with iron deficiency anemia, gastrointestinal bleeding must be excluded—approximately 62% have GI lesions 1

Clinical Context Matters

The interpretation depends heavily on patient demographics and clinical context:

• Premenopausal women: Menstrual blood loss is common cause 1
• Men and postmenopausal women: Investigate for GI bleeding, malignancy 1
• Chronic kidney disease patients: Likely erythropoietin deficiency 1
• Elderly patients: Consider anemia of chronic disease, nutritional deficiencies, or "unexplained anemia" 4