Which formula calculates MCH?

Which formula calculates MCH?

• A. Hb (g/dl) x 100 / PCV%
• B. Hb (g/dl) x 10 / Total RBC count
• C. Hb x Total RBC / 10
• D. Hb (g/dl) x PCV / 10

Answer: (B)

Mean corpuscular hemoglobin tells you how much hemoglobin is contained in each red blood cell. To get that value, relate the total hemoglobin in blood to how many red cells are carrying it. Use the Hb concentration in g/dL and the RBC count (in millions per microliter); multiply by 10 to convert the units so the result represents the hemoglobin per cell in picograms. That gives MCH = Hb (g/dL) × 10 / RBC count (million/µL). This is why the formula Hb (g/dL) × 10 / Total RBC count is the correct choice. The other forms mix in different parameters (for example, hematocrit/PCV for a component related to MCHC, or multiply/divide by different factors) and don’t produce the average Hb per cell the way MCH requires. If you plug in numbers, you’ll see how dividing Hb by RBC count alone would understate per-cell Hb without the ×10 adjustment, and using PCV instead of RBC count targets a different index.

Mean corpuscular hemoglobin tells you how much hemoglobin is contained in each red blood cell. To get that value, relate the total hemoglobin in blood to how many red cells are carrying it. Use the Hb concentration in g/dL and the RBC count (in millions per microliter); multiply by 10 to convert the units so the result represents the hemoglobin per cell in picograms. That gives MCH = Hb (g/dL) × 10 / RBC count (million/µL). This is why the formula Hb (g/dL) × 10 / Total RBC count is the correct choice.

The other forms mix in different parameters (for example, hematocrit/PCV for a component related to MCHC, or multiply/divide by different factors) and don’t produce the average Hb per cell the way MCH requires. If you plug in numbers, you’ll see how dividing Hb by RBC count alone would understate per-cell Hb without the ×10 adjustment, and using PCV instead of RBC count targets a different index.