What does MCHC (Mean Corpuscular Hemoglobin Concentration) value mean on a Complete Blood Count (CBC) test?

Understanding MCHC Value on CBC

MCHC (Mean Corpuscular Hemoglobin Concentration) is a measurement of the average concentration of hemoglobin inside a single red blood cell, expressed in grams per deciliter (g/dL) or grams per liter (g/L). It represents how much hemoglobin is packed into a given volume of red blood cells.

What MCHC Tells Us

MCHC is calculated using the following formula:

• MCHC = Hemoglobin (Hb) ÷ Hematocrit (Hct) × 100

The normal reference range for MCHC is typically:

• 32-36 g/dL (320-360 g/L)

Clinical Significance of Abnormal MCHC Values

Low MCHC (Hypochromia)

• Indicates decreased hemoglobin concentration within red blood cells
• Most commonly seen in:
  • Iron deficiency anemia 1
  • Thalassemia
  • Anemia of chronic disease (in some cases)
  • Lead poisoning

High MCHC (Hyperchromia)

• Physiologically, values significantly above the reference range are not possible due to limitations on hemoglobin solubility 2
• When seen, usually indicates:
  • Laboratory artifact or measurement error
  • Spherocytosis (hereditary or acquired)
  • Severe burns
  • Certain hemolytic anemias

MCHC in Context of Other RBC Indices

MCHC should always be interpreted alongside other CBC parameters:

1. Mean Cell Volume (MCV): Average size of red blood cells

   • Low MCV + Low MCHC: Strongly suggests iron deficiency anemia 1
   • Low MCV + Normal MCHC: May indicate thalassemia minor 1
   • Normal MCV + Low MCHC: Can occur in early iron deficiency or mixed deficiency states

2. Red Blood Cell Distribution Width (RDW): Measures variation in red blood cell size

   • Low MCV + High RDW (>14.0%) + Low MCHC: Characteristic of iron deficiency anemia 1
   • Low MCV + Normal RDW (≤14.0%) + Normal/Low MCHC: More suggestive of thalassemia minor 1

3. Mean Corpuscular Hemoglobin (MCH): Average amount of hemoglobin per red blood cell

   • Often parallels changes in MCHC but can vary independently

Diagnostic Value of MCHC

Recent research indicates MCHC has fair diagnostic accuracy for iron deficiency:

• A 2024 study showed MCHC had an area under the ROC curve of 0.71 for detecting iron deficiency in adolescents 3
• MCHC values are significantly lower in patients with iron deficiency compared to those without 3

Technical Considerations

Several factors can affect MCHC measurement:

• Cold agglutinins, lipemia, and hemolysis can interfere with accurate MCHC determination 4
• Modern automated analyzers have improved accuracy but may still produce spurious results in certain conditions 5, 4
• High triglyceride levels can sometimes trigger "turbidity" warnings and affect MCHC readings 6

Clinical Application

When evaluating MCHC:

1. Check for flags or warnings from the analyzer that might indicate spurious results
2. Compare with previous values when available
3. Interpret in context of other CBC parameters (MCV, RDW, MCH)
4. Consider confirmatory testing for suspected conditions:
   • Iron studies for suspected iron deficiency
   • Hemoglobin electrophoresis for suspected hemoglobinopathies
   • Peripheral blood smear review for morphological confirmation

Common Pitfalls

• Relying on MCHC alone for diagnosis without considering other parameters
• Failing to recognize spuriously high MCHC values that exceed physiological possibility
• Not considering pre-analytical variables (sample handling, storage conditions)
• Overlooking the need for peripheral smear review when MCHC is abnormal, especially when elevated 2

MCHC remains a valuable parameter in the evaluation of anemia when interpreted correctly within the context of other laboratory findings and clinical presentation.