Mean corpuscular hemoglobin concentration

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

The mean corpuscular hemoglobin concentration (MCHC) is a measure of the concentration of

hemoglobin
in a given volume of packed red blood cell.

It is calculated by dividing the hemoglobin by the

hematocrit. Reference ranges for blood tests are 32 to 36 g/dL (320 to 360g/L),[1] or between 4.81 and 5.58 mmol/L. It is thus a mass or molar concentration. Still, many instances measure MCHC in percentage (%), as if it were a mass fraction (mHb / mRBC).[2][3] Numerically, however, the MCHC in g/dL and the mass fraction of hemoglobin in red blood cells in % are identical, assuming an RBC density of 1g/mL and negligible hemoglobin in plasma.[citation needed
]

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 ("hyperchromic") in

homozygous hemoglobin C disease, depending upon the hemocytometer.[4][5] 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 count) or when there is opacification of the plasma (falsely increasing the measured hemoglobin). Causes of plasma opacification that can falsely increase the MCHC include hyperbilirubinemia, hypertriglyceridemia, and free hemoglobin in the plasma (due to hemolysis).[citation needed
]

Complicating conditions

Because of the way

cold agglutinin, or there may be some other problem resulting in one or more artifactual results affecting the MCHC.[citation needed
]

For example, for some patients with cold agglutinins, when their blood gets colder than 37 °C, the red cells will clump together. As a result, the analyzer may incorrectly report a low number of very dense red blood cells. This will result in an impossibly high number when the analyzer calculates the MCHC. This problem is usually picked up by the laboratory before the result is reported. The blood can be warmed until the cells separate from each other, and quickly put through the machine while still warm.[citation needed]

There are four steps to perform when a suspect increased MCHC (>370 g/L or >37.0 g/dL) is received from the analyzer:[citation needed]

  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
    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)

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. ^ Blood Test Results - Normal Ranges Archived 2012-11-02 at the Wayback Machine Bloodbook.Com. Retrieved on Jan 7, 2009
  3. ^ MedicineNet > Definition of MCHC Archived 2011-08-06 at the Wayback Machine Last Editorial Review: 7/21/1999
  4. PMID 20431699
    .
  5. ISBN 978-1-84214-147-2
    .

External links
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