What is the significance of a slightly elevated RBC count with low MCH and MCHC values, and how should it be managed?

Evaluation and Management of Elevated RBC with Low MCH and MCHC

The combination of elevated RBC count with low MCH and MCHC values most likely indicates iron deficiency, which requires further evaluation for underlying causes and iron supplementation therapy. 1

Laboratory Findings Analysis

• The patient's CBC shows elevated RBC (5.86 x10^6/uL), low MCH (25.8 pg), and low MCHC (31.1 g/dL), with normal hemoglobin (15.1 g/dL), normal MCV (83 fL), and normal RDW (14.7%) 1
• This pattern of high RBC count with low MCH/MCHC suggests a compensatory increase in red cell production in the setting of inadequate iron availability for hemoglobin synthesis 1, 2
• The normal MCV with low MCH/MCHC can occur in early iron deficiency before microcytosis develops, or when microcytosis and macrocytosis coexist (neutralizing each other) 1

Differential Diagnosis

• Iron deficiency: Most likely diagnosis given the laboratory pattern; can present with normal MCV in early stages while MCH and MCHC decrease first 1
• Polycythemia vera with iron deficiency: Elevated RBC with microcytic indices can occur in PV patients who develop iron deficiency 1, 3
• Thalassemia trait: Can present with elevated RBC and low MCH/MCHC, but typically shows more pronounced microcytosis (MCV <70) 3
• Anemia of chronic disease: Can present with low MCH/MCHC but typically not with elevated RBC count 1

Recommended Diagnostic Workup

1. Iron studies (essential first step):

   • Serum ferritin (most powerful test for iron deficiency) 1
   • Transferrin saturation 1
   • Serum iron 1

2. Additional tests if iron deficiency is confirmed:

   • Reticulocyte count to assess bone marrow response 1
   • CRP to evaluate for inflammation (which can affect ferritin interpretation) 1
   • Vitamin B12 and folate levels to rule out concurrent deficiencies 1

3. If iron deficiency is confirmed in adult male or post-menopausal female:

   • Upper GI endoscopy with small bowel biopsy 1
   • Colonoscopy or barium enema 1
   • These tests are crucial as GI malignancy is a common cause of iron deficiency in these populations 1

4. If polycythemia vera is suspected:

   • Serum erythropoietin level 1
   • Consider bone marrow examination if clinically indicated 1

Management Approach

1. Treat underlying cause:

   • If gastrointestinal source of blood loss is identified, appropriate intervention is required 1
   • If malabsorption (e.g., celiac disease) is diagnosed, disease-specific treatment 1

2. Iron supplementation:

   • Oral iron therapy (ferrous sulfate 325 mg three times daily or equivalent) 1
   • Continue for 3-6 months after normalization of hemoglobin to replenish iron stores 1
   • Monitor response with repeat CBC after 4-8 weeks of therapy 1, 2

3. Follow-up:

   • Reassess CBC and iron studies after 3 months of treatment 1
   • If no improvement in MCH/MCHC despite adequate iron supplementation, consider alternative or additional diagnoses 1, 2

Important Considerations and Pitfalls

• Serum ferritin can be falsely elevated in inflammatory states, making iron deficiency diagnosis challenging; values up to 100 μg/L may still be consistent with iron deficiency in the presence of inflammation 1
• Normal MCV does not rule out iron deficiency, especially in early stages or when concurrent B12/folate deficiency exists 1
• Elevated RBC with low MCH/MCHC can be an early sign of polycythemia vera with iron deficiency; don't miss this diagnosis, especially if iron replacement doesn't normalize indices 1, 3
• In men and post-menopausal women, iron deficiency should always prompt investigation for gastrointestinal malignancy, even with mild laboratory abnormalities 1