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It is calculated by dividing the haemoglobin by the [[haematocrit]]. [[Reference ranges for blood tests]] are 32 to 36 g/dL,<ref>{{MedlinePlusEncyclopedia|003648|RBC indices}}</ref> or between 19.9 <ref name=Wallach>Converted with conversion factor from ({{cite book |last=Wallach |first=Jacques Burton |date=2007 |title=Interpretation of Diagnostic Tests |url=https://books.google.com/books?id=FCbXDdOvB9IC&pg=PA1123&dq=mchc+0.6206 |publisher=Lippincott Williams & Wilkins}}). 1 g/dL = 0.6206&nbsp;mmol/L</ref> and 22.3<ref name=Wallach/> mmol/L. It is thus a mass or molar concentration.
It is calculated by dividing the haemoglobin by the [[haematocrit]]. [[Reference ranges for blood tests]] are 32 to 36 g/dL,<ref>{{MedlinePlusEncyclopedia|003648|RBC indices}}</ref> or between 19.9 <ref name=Wallach>Converted with conversion factor from ({{cite book |last=Wallach |first=Jacques Burton |date=2007 |title=Interpretation of Diagnostic Tests |url=https://books.google.com/books?id=FCbXDdOvB9IC&pg=PA1123&dq=mchc+0.6206 |publisher=Lippincott Williams & Wilkins}}). 1 g/dL = 0.6206&nbsp;mmol/L</ref> and 22.3<ref name=Wallach/> mmol/L. It is thus a mass or molar concentration.
Still, many instances<ref name=bloodbook>[http://www.bloodbook.com/ranges.html Blood Test Results - Normal Ranges] Bloodbook.Com. Retrieved on Jan 7, 2009</ref><ref name=medicinenet>[http://www.medterms.com/script/main/art.asp?articlekey=9994 MedicineNet > Definition of MCHC] Last Editorial Review: 7/21/1999</ref> measure MCHC in [[percentage]] (%), as if it were a [[Mass fraction (chemistry)|mass fraction]] (m<sub>Hb</sub> / m<sub>RBC</sub>). Numerically, however, the MCHC in g/dL and the mass fraction of haemoglobin in red blood cells in % are identical, assuming a RBC [[density]] of 1g/mL and negligible haemoglobin in plasma.
Still, many instances<ref name=bloodbook>[http://www.bloodbook.com/ranges.html Blood Test Results - Normal Ranges] Bloodbook.Com. Retrieved on Jan 7, 2009</ref><ref name=medicinenet>[http://www.medterms.com/script/main/art.asp?articlekey=9994 MedicineNet > Definition of MCHC] Last Editorial Review: 7/21/1999</ref> measure MCHC in [[percentage]] (%), as if it were a [[Mass fraction (chemistry)|mass fraction]] (m<sub>Hb</sub> / m<sub>RBC</sub>). Numerically, however, the MCHC in g/dL and the mass fraction of haemoglobin in red blood cells in % are identical, assuming an RBC [[density]] of 1g/mL and negligible haemoglobin in plasma.


==Interpretation==
==Interpretation==

Revision as of 09:21, 22 February 2018

Not to be confused with mean corpuscular hemoglobin per erythrocyte, although they are predictably correlated in healthy states.
hemoglobin

The Mean corpuscular hemoglobin concentration, a measure of the concentration of haemoglobin in a given volume of packed red blood cells. It is reported as part of a standard complete blood count.

It is calculated by dividing the haemoglobin by the haematocrit. Reference ranges for blood tests are 32 to 36 g/dL,[1] or between 19.9 [2] and 22.3[2] mmol/L. It is thus a mass or molar concentration. Still, many instances[3][4] measure MCHC in percentage (%), as if it were a mass fraction (mHb / mRBC). Numerically, however, the MCHC in g/dL and the mass fraction of haemoglobin in red blood cells in % are identical, assuming an RBC density of 1g/mL and negligible haemoglobin in plasma.

Interpretation

A low MCHC can be interpreted as identifying decreased production of hemoglobin. MCHC can be normal even when hemoglobin production is decreased (such as in iron deficiency) due to a calculation artifact. MCHC can be elevated ("polychromatic") in hereditary spherocytosis, sickle cell disease and homozygous haemoglobin C disease, depending upon the hemocytometer.[5][6] MCHC can be elevated in some megaloblastic anemias. MCHC can be falsely elevated when there is agglutination of red cells (falsely lowering the measured RBC) or when there is opacifaction of the plasma (falsely increasing the measured hemoglobin). Causes of plasma opacification that can falsely increase the MCHC include hyperbilirubinemia, hypertryglyceridemia, and free hemoglobin in the plasma (due to hemolysis).

Complications with cold agglutinin

Because of the way automated analysers count blood cells, a very high MCHC (greater than about 370 g/L) may indicate the blood is from someone with a cold agglutinin. This means that when their blood gets colder than 37 °C it starts to clump together. As a result, the analyzer may incorrectly report a low number of very dense red blood cells for blood samples in which agglutination has occurred.

This problem is usually picked up by the laboratory before the result is reported. The blood is warmed until the cells separate from each other, and quickly put through the machine while still warm. This is the most sensitive test for iron deficiency anaemia.

There are four steps to perform when an increase MCHC(>370 g/L or 37.0 g/dL) is received from the analyzer:

  1. Remix the EDTA tube—if the MCHC corrects, report corrected results
  2. Incubation at 37 °C—if the MCHC corrects, report corrected results and comment on possible cold agglutinin
  3. Saline replacement: Replace plasma with same amount of saline to exclude interference e.g. Lipemia and Auto-immune antibodies—if the MCHC corrects, report corrected results and comment on Lipemia
  4. Check the slide for spherocytosis (e.g. in hereditary spherocytosis, among other causes)

Auto-agglutination: Falsely ↓RBC and ↑MCV

Lipaemia: Falsely ↑haemoglobin.

Haemolysis: Will falsely increase the MCHC (measured haemoglobin is proportionally higher than HCT or PCV) and falsely decrease the calculated haemoglobin (fewer intact RBC)

Other: Heinz bodies (many, particularly if large) may falsely increase the MCHC but not the MCH. Agglutination: Falsely increases the MCHC (measured haemoglobin is proportionally higher than HCT). The MCH is more accurate in this setting. Excess EDTA: Dehydrates RBC, falsely increasing MCHC and MCH.

Worked example

Measure Units Conventional units Conversion
Hct 40%
Hb 100 grams/liter 10 grams/deciliter (deci- is 10−1)
RBC 5E+12 cells/liter 5E+6 cells/μL (micro is 10−6)
MCV = (Hct/100) / RBC 8E-14 liters/cell 80 femtoliters/cell (femto- is 10−15)
MCH = Hb / RBC 2E-11 grams/cell 20 picograms/cell (pico- is 10−12)
MCHC = Hb / (Hct/100) 250 grams/liter 25 grams/deciliter (deci is 10−1)

See also

References

  1. ^ MedlinePlus Encyclopedia: RBC indices
  2. ^ a b Converted with conversion factor from (Wallach, Jacques Burton (2007). Interpretation of Diagnostic Tests. Lippincott Williams & Wilkins.). 1 g/dL = 0.6206 mmol/L
  3. ^ Blood Test Results - Normal Ranges Bloodbook.Com. Retrieved on Jan 7, 2009
  4. ^ MedicineNet > Definition of MCHC Last Editorial Review: 7/21/1999
  5. ^ Hill, Valerie L.; Simpson, Virginia Z.; Higgins, Jeanette M.; Hu, Zonghui; Stevens, Randy A.; Metcalf, Julie A.; Baseler, Michael (2017-01-28). "Evaluation of the Performance of the Sysmex XT-2000i Hematology Analyzer With Whole Bloods Stored at Room Temperature". Laboratory medicine. 40 (12): 709–718. doi:10.1309/T0FJYP2RBXEHX4. ISSN 0007-5027. PMC 2860627. PMID 20431699.
  6. ^ Rifkind, David; Cohen, Alan S. (2002). The Pediatric Abacus. Informa Healthcare. p. 54. ISBN 1-84214-147-3.
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