What is the cause of anemia in a patient with low red blood cell count, low hemoglobin, and low hematocrit, but normal white blood cell count and platelet count, and how should it be managed?

Interpretation: Mild Normocytic Anemia with Lymphopenia

You have mild normocytic anemia (hemoglobin 11.4 g/dL, hematocrit 34.4%, RBC 3.84) with normal red cell indices (MCV, MCH, MCHC all normal), indicating this is NOT iron deficiency anemia, and you also have mild lymphopenia (absolute lymphocytes 804). 1

Understanding Your Results

The Anemia Component

Your anemia is classified as:

• Mild (hemoglobin 11.4 g/dL is above 11.0 but below normal for adults) 2
• Normocytic (MCV 89.6 is normal, meaning red blood cells are normal size) 2, 1
• Normochromic (MCHC 33.1 is normal, meaning normal hemoglobin concentration in cells) 2

This pattern excludes iron deficiency anemia as the primary cause, since iron deficiency typically causes low MCV (microcytic) and eventually low MCHC (hypochromic). 3, 4

The Lymphopenia

Your absolute lymphocyte count of 804 cells/μL is below the normal range (typically >1000), while your neutrophil percentage is elevated at 81.4% (relative lymphopenia with neutrophil predominance). 2

Required Diagnostic Workup

Before any treatment can be initiated, you need a comprehensive evaluation to identify the underlying cause: 1

Essential Laboratory Tests

• Iron studies (serum ferritin, transferrin saturation, serum iron, TIBC) to assess for functional iron deficiency or anemia of chronic disease, even though your indices are normal 2, 1
• Reticulocyte count to determine if your bone marrow is responding appropriately to the anemia (low count suggests production problem, elevated suggests blood loss or hemolysis) 2, 1
• Vitamin B12 and folate levels to exclude early nutritional deficiencies that can present with normocytic anemia before becoming macrocytic 1
• Kidney function tests (creatinine, GFR) since chronic kidney disease is a common cause of normocytic anemia due to erythropoietin deficiency 2, 1
• C-reactive protein (CRP) or other inflammatory markers to identify anemia of chronic disease/inflammation 1

Additional Investigations to Consider

• Stool guaiac test for occult gastrointestinal bleeding 2
• Thyroid function tests if clinically indicated 1
• Peripheral blood smear to evaluate red cell morphology and assess for other abnormalities 2, 1

Most Likely Causes in Your Case

Given normocytic anemia with normal white blood cell and platelet counts:

1. Anemia of chronic disease/inflammation - most common cause of normocytic anemia, often associated with elevated ferritin but low transferrin saturation (functional iron deficiency) 1
2. Early iron deficiency - can present with normal indices initially before MCV drops 4
3. Chronic kidney disease - causes normocytic anemia through decreased erythropoietin production 2, 1
4. Occult blood loss - chronic slow bleeding can cause normocytic anemia 1
5. Combined deficiencies - iron deficiency masked by concurrent B12/folate deficiency can present with normal MCV 5, 3

Management Approach

Do NOT Start Empiric Treatment

You should not receive iron supplementation or any other treatment without first confirming the specific deficiency and underlying cause. 5, 1 Treating empirically can mask the true diagnosis and delay appropriate management.

When to Refer to Hematology

Immediate hematology referral is warranted if: 1

• Abnormalities develop in multiple cell lines (your lymphopenia warrants monitoring)
• No response to appropriate therapy once cause is identified
• Unexplained normocytic anemia after complete workup

Monitoring Plan

• Repeat CBC in 3 months if workup reveals chronic kidney disease or chronic disease 1
• Repeat CBC in 4-8 weeks after starting treatment once cause is identified 1, 3

Critical Pitfalls to Avoid

• Do not assume this is iron deficiency - your normal MCV and MCHC make typical iron deficiency unlikely 3
• Do not overlook the lymphopenia - this may indicate an underlying chronic inflammatory or infectious process contributing to your anemia 2
• Do not ignore combined deficiencies - iron deficiency can coexist with B12/folate deficiency, masking typical findings 5, 3
• Ferritin can be falsely elevated in inflammation - making iron deficiency diagnosis challenging even if ferritin appears normal 3

Next Steps

1. Schedule follow-up with your physician to order the complete workup listed above 1
2. Provide detailed history of any chronic medical conditions, medications, dietary habits, menstrual history (if applicable), and symptoms like fatigue or bleeding 2, 1
3. Do not start over-the-counter iron supplements until iron deficiency is confirmed with laboratory testing 1, 3