What is the diagnosis and management for a patient with low Mean Corpuscular Hemoglobin (MCH), low Mean Corpuscular Hemoglobin Concentration (MCHC), high Red Cell Distribution Width (RDW), and low Mean Platelet Volume (MPV)?

Diagnosis and Management of Low MCH, Low MCHC, High RDW, and Low MPV

The combination of low Mean Corpuscular Hemoglobin (MCH), low Mean Corpuscular Hemoglobin Concentration (MCHC), high Red Cell Distribution Width (RDW), and low Mean Platelet Volume (MPV) strongly indicates iron deficiency anemia and requires iron supplementation therapy with investigation for underlying causes. 1

Diagnostic Interpretation

• Low MCH and MCHC indicate hypochromia, which is a reliable marker of iron deficiency, as these parameters reflect reduced hemoglobin content in red blood cells 1
• High RDW (>14.0%) combined with low MCH/MCHC strongly suggests iron deficiency anemia rather than thalassemia minor, as iron deficiency typically causes greater variation in red blood cell size 1
• Low MPV can be associated with iron deficiency, though this parameter is less commonly discussed in guidelines compared to other red cell indices 2

Differential Diagnosis

• Iron Deficiency Anemia: Most likely diagnosis based on the pattern of low MCH/MCHC with high RDW 1
• Thalassemia Minor: Less likely with high RDW (typically has RDW ≤14.0% with low MCV/MCH) 1
• Anemia of Chronic Disease: Can present with low MCH/MCHC but typically has normal RDW 1
• Combined Nutritional Deficiencies: Consider if other laboratory abnormalities are present 1

Diagnostic Algorithm

1. Confirm iron deficiency with serum ferritin (most specific test):

   • Ferritin <15 μg/L indicates absent iron stores 1
   • Ferritin <30 μg/L indicates low body iron stores 1
   • In presence of inflammation, ferritin up to 100 μg/L may still be consistent with iron deficiency 1

2. Additional iron studies if ferritin is equivocal:

   • Transferrin saturation (low in iron deficiency) 1
   • Serum iron (low in iron deficiency) 1
   • Erythrocyte protoporphyrin (elevated in iron deficiency) 1

3. Rule out other causes:

   • Hemoglobin electrophoresis to exclude thalassemia if iron studies are normal 1
   • Check vitamin B12 and folate levels 1
   • Evaluate for chronic inflammatory conditions 1

Management Approach

1. Iron supplementation:

   • Oral iron therapy is first-line treatment (ferrous sulfate, ferrous gluconate, or ferrous fumarate) 1
   • Monitor response: A good response (Hb rise ≥10 g/L within 2 weeks) confirms iron deficiency diagnosis 1

2. Investigate underlying cause of iron deficiency:

   • GI evaluation is warranted in adults, especially men and non-menstruating women 1
   • Consider endoscopic evaluation (upper and lower GI) based on symptoms and severity 1
   • Assess for other sources of blood loss 1

3. Follow-up monitoring:

   • Check hemoglobin and red cell indices after 2-4 weeks of iron therapy 1
   • Continue iron therapy for 3-6 months after normalization of hemoglobin to replenish iron stores 1

Clinical Pearls and Pitfalls

• MCH may be a more reliable marker of iron deficiency than MCV as it is less dependent on storage and counting machine used 1
• RDW has high sensitivity (62.5-75%) for detecting iron, folate, and B12 deficiencies but lacks specificity for determining the type of deficiency 3
• In the presence of inflammation, serum ferritin may appear normal despite iron deficiency, making diagnosis challenging 1
• The combination of red cell parameters (MCH, MCHC, RDW) provides better diagnostic accuracy than any single parameter alone 2, 4
• Avoid relying solely on MCV for diagnosis, as microcytosis alone has limited sensitivity for detecting iron deficiency 5, 6