MCHC Calculator (Mean Corpuscular Haemoglobin Concentration)
MCHC Calculator (Mean Corpuscular Haemoglobin Concentration)
Calculate MCHC from haemoglobin and haematocrit, and learn why a genuinely high result is rare enough to demand a blood film first.
MCHC
Haemoglobin concentrationHaemoglobin 12.5 g/dL, haematocrit 38%
Formula
- Hb
- haemoglobin concentration in g/dL
- Hct
- haematocrit, the packed red cell volume as a percentage of whole blood
- result
- g/dL — the average haemoglobin concentration within the red cell mass, independent of how many cells or how big they are
Worked example
Haemoglobin 12.5 g/dL, haematocrit 38%
12.5 ÷ 38 = 0.32895
0.32895 × 100 = 32.9 g/dL
High MCHC — genuine versus analytical
| Cause | Genuine or analytical | Mechanism |
|---|---|---|
| Hereditary spherocytosis | Genuine | Loss of membrane relative to cell volume concentrates haemoglobin |
| Autoimmune haemolytic anaemia with spherocytes | Genuine | Partial membrane loss to splenic macrophages produces spherocytes |
| Cold agglutinin disease | Both | Red cell clumping falsely lowers RBC and falsely raises both MCV and MCHC |
| Lipaemia, marked hyperbilirubinaemia | Analytical | Interferes with spectrophotometric haemoglobin measurement |
| Very high white cell count | Analytical | Turbidity from white cells is read as extra haemoglobin |
| In-vitro haemolysis | Analytical | Free haemoglobin is measured but the cell count denominator has already fallen |
Why a high MCHC is a prompt to look, not a diagnosis
MCHC expresses haemoglobin concentration within the red cell mass rather than the mass or volume of an individual cell, and there is a physical ceiling on how concentrated haemoglobin can be before it crystallises within the cell. That ceiling makes a genuinely high MCHC uncommon, and its differential is correspondingly short: hereditary spherocytosis, autoimmune haemolytic anaemia with spherocytes, and cold agglutinin disease. In each, the red cell has lost surface membrane relative to its haemoglobin content — a spherocyte is a smaller sphere carrying the same haemoglobin as the biconcave disc it was made from, so the concentration rises.
Before accepting a high MCHC as biological, the analytical causes need to be excluded, because they are more common than the genuine ones. Lipaemia, marked hyperbilirubinaemia and a very high white cell count all interfere with the spectrophotometric measurement of haemoglobin and inflate the numerator. In-vitro haemolysis releases free haemoglobin while the red cell count denominator has already fallen, which raises the ratio without any true change in the patient. Cold agglutinins cause the red cells to clump in the counting chamber, which the analyser reads as fewer, larger cells — falsely lowering the RBC and falsely raising both MCV and MCHC simultaneously, a pattern that is a useful clue in itself. An MCHC above about 36.5 g/dL should prompt a look at the sample for clots or clumping and a blood film for spherocytes, not an immediate diagnosis of haemolysis.
Frequently asked questions
What does a high MCHC mean?
Most often an analytical artefact — lipaemia, marked hyperbilirubinaemia, a very high white cell count, in-vitro haemolysis, or cold agglutinin clumping. Genuine causes are hereditary spherocytosis, autoimmune haemolytic anaemia with spherocytes, and cold agglutinin disease.
Why is a genuinely high MCHC rare?
There is a physical limit to how concentrated haemoglobin can be within a red cell before it crystallises, so true hyperchromia only occurs when the cell has lost membrane relative to its haemoglobin content, as in spherocytosis.
What does cold agglutinin disease do to MCHC?
The agglutinins clump red cells together, which the analyser miscounts as fewer, larger cells. This falsely lowers the RBC and falsely raises both MCV and MCHC. Warming the sample before re-running it usually corrects the artefact.
At what MCHC should I request a blood film?
Above roughly 36.5 g/dL. Check first for an obvious analytical cause — lipaemia, jaundice, a very high white count, or clumping — then examine the film for spherocytes before considering a haemolytic diagnosis.
Related calculators
References
- Hoffbrand AV, Steensma DP. Hoffbrand’s Essential Haematology. 8th ed.
- Bain BJ. Diagnosis from the blood smear. N Engl J Med. 2005;353(5):498–507.