What does a mean corpuscular hemoglobin (MCH) of 25.2 pg and mean corpuscular hemoglobin concentration (MCHC) of 31.1 g/dL indicate, and what are the appropriate next steps in evaluation and management?

Low MCH and Normal MCHC: Hypochromic Microcytic Anemia

Your MCH of 25.2 pg is low (normal range typically 27-33 pg) and MCHC of 31.1 g/dL is at the lower end of normal (normal range 32-36 g/dL), indicating hypochromic microcytic anemia that requires immediate iron studies to confirm iron deficiency and guide further investigation.

What These Values Mean

The reduced MCH indicates hypochromia (decreased hemoglobin content per red blood cell), while the borderline-low MCHC confirms reduced hemoglobin concentration within red cells 1. MCH is actually a more reliable marker than MCV for detecting iron deficiency because it's less dependent on the analyzer used and is reduced in both absolute and functional iron deficiency 1.

Immediate Next Steps

1. Confirm Iron Deficiency with Serum Ferritin

• Order serum ferritin immediately - this is the single most useful marker for iron deficiency 1
• Ferritin <15 μg/L is highly specific (99%) for iron deficiency 1
• Ferritin <30 μg/L generally indicates low iron stores 1
• Ferritin <45 μg/L warrants consideration of investigation, especially with chronic inflammation (specificity 92%) 1

Critical caveat: Ferritin is an acute phase protein and can be falsely normal with concurrent inflammation. If ferritin is 45-150 μg/L and inflammation is suspected, add transferrin saturation to the workup 1.

2. Complete the Iron Panel

• Transferrin saturation (helpful if ferritin is equivocal)
• Total iron-binding capacity
• Complete blood count with MCV to assess microcytosis 1

3. Rule Out Alternative Diagnoses

If iron studies are normal or equivocal, consider:

• Hemoglobin electrophoresis - essential to exclude thalassemia, particularly if there's appropriate ethnic background (Mediterranean, Asian, African descent) 1
• Thalassemia typically shows MCV reduced out of proportion to anemia 1
• The MCH cut-off of <25 pg has been used in thalassemia screening, though your value of 25.2 pg is borderline 2

Diagnostic Algorithm Based on Ferritin Results

If Ferritin <15 μg/L:

• Diagnose iron deficiency anemia
• Investigate for source of blood loss or malabsorption
• Consider GI investigation at any level of anemia with confirmed iron deficiency 1

If Ferritin 15-45 μg/L:

• Likely iron deficiency, especially without inflammation
• Consider therapeutic trial of iron supplementation
• A hemoglobin rise ≥10 g/L within 2 weeks is highly suggestive of absolute iron deficiency, even if iron studies are equivocal 1

If Ferritin >45 μg/L:

• Check transferrin saturation
• Consider hemoglobin electrophoresis to exclude thalassemia 1
• Evaluate for anemia of chronic disease
• Consider genetic disorders of iron metabolism if ferritin and/or transferrin saturation are elevated 3

Investigation for Underlying Cause

Once iron deficiency is confirmed, investigation should be considered at any level of anemia in the presence of iron deficiency, with stronger indication for more severe anemia 1. The threshold for fast-track GI investigation varies, but don't wait for severe anemia if iron deficiency is documented.

Common Pitfalls to Avoid

• Don't rely solely on MCV - MCH is more sensitive and reliable for iron deficiency 1
• Don't miss thalassemia - always check hemoglobin electrophoresis if microcytosis persists with normal iron studies 1
• Don't accept "normal" ferritin at face value - values up to 45 μg/L may still represent iron deficiency, especially with inflammation 1
• Don't delay investigation - any degree of iron deficiency anemia warrants evaluation for underlying pathology 1