What is the difference between Mean Corpuscular Hemoglobin (MCH) and Mean Corpuscular Hemoglobin Concentration (MCHC)?

Difference Between MCH and MCHC in Hematology

Mean Corpuscular Hemoglobin (MCH) measures the average amount of hemoglobin per red blood cell, while Mean Corpuscular Hemoglobin Concentration (MCHC) measures the average concentration of hemoglobin within a given volume of packed red blood cells. 1

Key Differences

Definition and Calculation

• MCH (Mean Corpuscular Hemoglobin):

  • Measures the absolute amount of hemoglobin in an average red blood cell
  • Calculated as: Hemoglobin (g/dL) ÷ RBC count (millions/μL) × 10
  • Units: picograms (pg) per cell

• MCHC (Mean Corpuscular Hemoglobin Concentration):

  • Measures the concentration of hemoglobin relative to the size of the cell
  • Calculated as: Hemoglobin (g/dL) ÷ Hematocrit (%) × 100
  • Can also be calculated as: MCH ÷ MCV × 100
  • Units: grams per deciliter (g/dL)

Clinical Significance

• MCH:

  • More sensitive for detecting early iron deficiency
  • Better at identifying changes in hemoglobin content
  • Area under ROC curve of 0.67-0.96 for diagnosing iron deficiency 2
  • May be more accurate than MCV in diagnosing iron deficiency 2

• MCHC:

  • More specific for certain conditions like hereditary spherocytosis
  • Less affected by cell size variations
  • Provides information about hemoglobin density within cells
  • Area under ROC curve of 0.68-0.87 for diagnosing iron deficiency 2

Diagnostic Value in Anemia Classification

Iron Deficiency Anemia

• Both MCH and MCHC are significantly lower in patients with iron deficiency 3
• MCH decreases earlier than MCHC in developing iron deficiency
• In a recent study, MCHC showed an area under the ROC curve of 0.71 for diagnosing iron deficiency in adolescents 3

Microcytic Anemias Differentiation

• MCH and MCHC values help differentiate between iron deficiency anemia and thalassemia:
  • Iron Deficiency: Low MCH, Low MCHC
  • Thalassemia: Low MCH, Normal MCHC 1

Vascular Disease Assessment

• Lower MCH and MCHC have been associated with vascular involvement in certain inflammatory conditions 4
• MCH and MCHC are negatively correlated with platelet count, plateletcrit, and neutrophil count 4

Pitfalls and Considerations

• Analytical Considerations:

  • MCHC is available in two forms: conventional computed value (Hgb/PCV) and direct measurement (CHCM) on some analyzers 5
  • MCHC is significantly greater than CHCM in patients with iron deficiency anemia, but not in other causes of microcytic anemia 5

• Diagnostic Limitations:

  • Neither parameter alone is sufficient for definitive diagnosis
  • Normal values do not exclude iron deficiency in anemic patients 2
  • At cutoff limits giving 90% sensitivity for detecting iron deficiency, specificity is only about 50% 2

• Clinical Application:

  • Should be interpreted alongside other parameters like MCV and RDW
  • Z-score analysis of MCH and MCHC can help screen for spurious results and predict anemia type 6
  • Both parameters should be considered in the context of a complete blood count and clinical presentation

When to Use Which Parameter

• Use MCH when:

  • Screening for early iron deficiency
  • Evaluating response to iron therapy
  • Assessing absolute hemoglobin content changes

• Use MCHC when:

  • Differentiating causes of microcytic anemia
  • Evaluating for hereditary spherocytosis
  • Assessing hemoglobin concentration within cells

Both parameters provide complementary information and are most valuable when interpreted together as part of a complete blood count analysis.