A High MCHC
Among the results on a blood count, this is one of the very few that is close to impossible for biological reasons. Hemoglobin cannot be packed into a red cell beyond a certain concentration without coming out of solution, so a value above that ceiling means one of two things: the cells really are unusually dense, which points at a specific inherited condition, or something interfered with the measurement. The second is commoner, and the laboratory can usually tell which.
The pattern on your report
- MCHC High Key
- MCV Normal Key
- Hemoglobin Normal Key
- Reticulocytes Normal Key
Printed as: Hemoglobin in g/Lor g/dL— Measured optically, which is why cloudy plasma from high triglycerides reads as extra hemoglobin.MCHC in g/Lor g/dL— Calculated rather than measured, by dividing hemoglobin by hematocrit, so an error in either inflates it.MCV in fL— A normal value here is part of what makes a raised MCHC notable, since the cells are ordinary in size but dense.Reticulocytes in x10^9/Lor x10^3/uL— Raised if red cells are being destroyed, which is what distinguishes a real finding from a sample problem.
Why the numbers look like this
MCHC is not measured. It is calculated by dividing the hemoglobin by the hematocrit, so anything that falsely raises the first or falsely lowers the second inflates the result.
Both errors happen for recognizable reasons. Very high triglycerides make the plasma milky, and because hemoglobin is measured optically, that cloudiness reads as extra hemoglobin. Cold agglutinins make red cells clump in a cooled sample, and the analyzer counts a clump as one cell, so the measured cell volume falls. Red cells ruptured in the tube release their hemoglobin into the plasma, where it is still measured but no longer occupies any cell volume.
The genuine biological cause works differently. In hereditary spherocytosis the cell membrane loses surface area, so the cell rounds up and its contents become more concentrated without any extra hemoglobin being made. The MCHC is the index that detects this, and it is often the only clue on an otherwise unremarkable count.
That makes a high MCHC unusual among blood count results: it is far more often a message about the sample than about the person, but the exception it points to is a real and treatable condition.
Not being flagged is not the same as normal
The upper end of the normal range sits close to the physical limit of how concentrated hemoglobin can be inside a cell, which is why values much above it are so suspicious. Analyzers differ in how they derive the underlying measurements, so the same sample can produce slightly different values on different machines. A result that is only marginally raised, with everything else normal, usually means nothing at all; a clearly raised one deserves the explanations above.
What else on the report can hide this
Ask whether the sample was lipemic or hemolyzed, since laboratories record both and either explains the result immediately.
A blood film settles the biological question. Spherocytes are visible to a person examining the slide, and their presence with a raised MCHC is a strong combination.
If spherocytes are present, the next question is whether they were inherited or acquired. The direct antiglobulin test answers it, turning positive in the immune form and negative in the hereditary one, and the two are managed differently.
Whether red cells are actually being destroyed is settled by haptoglobin, LDH, a split bilirubin and the reticulocyte count together, and that is what turns an index into a diagnosis.
If the sample is suspected of clumping in the cold, repeating it with the blood kept warm from collection to analysis resolves it. That is a specific request rather than something a laboratory does routinely.
What usually causes it
Listed from most to least common — not from most to least serious.
- Very common
A lipemic sample
Very high triglycerides cloud the plasma, and the optical hemoglobin measurement reads that cloudiness as extra hemoglobin. The laboratory records it.
- Very common
Red cells ruptured in the tube
Hemoglobin released into the plasma is still measured but occupies no cell volume, so the ratio rises. Usually flagged as hemolyzed.
- Very common
A marginally raised value with everything else normal
Analyzers derive this differently and a small excess means nothing. Only a clearly raised value warrants the explanations below.
- Common
Cold agglutinins
Cells clump in a cooled sample and the analyzer counts each clump as one cell. Repeating with the sample kept warm resolves it, and that has to be requested.
- Common
Hereditary spherocytosis
The genuine biological cause. Membrane surface area is lost, the cell rounds up, and its contents concentrate. Often the only clue on an otherwise ordinary count.
- Uncommon
Autoimmune hemolysis
Also produces spherocytes, but acquired. A positive direct antiglobulin test separates it, and the treatment is entirely different.
- Uncommon
A very high white cell count
Interferes with the hematocrit measurement on some analyzers. Suspected when the white count is markedly raised.
- Rare
Severe burns
Red cell fragments and altered membranes produce a genuinely raised value. The clinical situation is not in doubt.
- Rare
Hemoglobin C disease — in people of West African ancestry
The hemoglobin crystallizes inside the cell, raising the concentration genuinely. Target cells on the film point to it.
What is usually checked next
- Ask whether the sample was lipemic or hemolyzed Laboratories record both, and either explains the result without any further test.
- A blood film Spherocytes are visible to a person examining the slide, and their presence with a raised MCHC is a strong combination.
- Direct antiglobulin test Positive in the acquired immune form and negative in the inherited one, and the two are managed differently.
- Haptoglobin, LDH, bilirubin and reticulocytes Settle whether red cells are actually being destroyed, which is what turns an index into a diagnosis.
- A repeat with the sample kept warm Resolves cold agglutinins, and it is a specific request rather than routine practice.
When to seek care sooner
- Emergency Sudden pallor, breathlessness at rest, or fainting
- Same day Yellowing of the eyes with dark urine
- Soon Pain in the left upper abdomen, or a known enlarged spleen
- Soon Fingers or toes turning white and painful in the cold
- Soon A falling hemoglobin alongside
- Soon Gallstones at a young age, or a family history of them
Questions worth bringing to your appointment
- Was the sample recorded as lipemic or hemolyzed?
- Has a blood film been looked at for spherocytes?
- Are my haptoglobin, LDH and reticulocytes normal?
- Could the sample have clumped in the cold?
- Is there anyone in my family with spherocytosis or early gallstones?