Mean corpuscular hemoglobin concentration
Encyclopedia
Hemoglobin
Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...
in a given volume of packed red blood cells. It is reported as part of a standard complete blood count
Complete blood count
A complete blood count , also known as full blood count or full blood exam or blood panel, is a test panel requested by a doctor or other medical professional that gives information about the cells in a patient's blood...
.
It is calculated by dividing the hemoglobin by the hematocrit
Hematocrit
The hematocrit or packed cell volume or erythrocyte volume fraction is the percentage of the concentration of red blood cells in blood. It is normally about 45% for men and 40% for women...
. Reference ranges for blood tests are 32 to 36 g/dl, or between 4.9 to 5.5 mmol/L. It is thus a mass or molar concentration.
Still, many instances measure MCHC in percentage
Percentage
In mathematics, a percentage is a way of expressing a number as a fraction of 100 . It is often denoted using the percent sign, “%”, or the abbreviation “pct”. For example, 45% is equal to 45/100, or 0.45.Percentages are used to express how large/small one quantity is, relative to another quantity...
(%), as if it was a mass fraction (mHb / mRBC). Numerically, however, the MCHC in g/dl and the mass fraction of hemoglobin in red blood cells in % are identical, assuming a RBC density
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
of 1g/mL and negligible hemoglobin in plasma.
Interpretation
MCHC is diminished ("hypochromic") in microcytic anemiaMicrocytic anemia
Microcytic anemia is a generic term for any type of anemia characterized by small red blood cells. The normal mean corpuscular volume is 76-100 fL, with smaller cells as macrocytic....
s, and normal ("normochromic
Normochromic
Normochromic is a form of anemia in which the concentration of hemoglobin in the red blood cells is within the standard range. However, there are insufficient numbers of red blood cells. This includes: aplastic, posthemorrhagic, and hemolytic anemias and anemia of chronic disease.synonymous with...
") in macrocytic anemias (due to larger cell size, though the hemoglobin amount or MCH is high, the concentration remains normal). MCHC is elevated ("hyperchromic") in hereditary spherocytosis
Hereditary spherocytosis
Hereditary spherocytosis is a genetically-transmitted form of spherocytosis, an auto-hemolytic anemia characterized by the production of red blood cells that are sphere-shaped rather than bi-concave disk shaped , and therefore more prone to hemolysis.-Symptoms:As in non-hereditary spherocytosis,...
, sickle cell disease and homozygous hemoglobin C disease.
This count is used to give a rough guide to what shade of red, RBC will be. (paler=lower than the standard)
Complications with cold agglutinin
Because of the way automated analyserAutomated analyser
An automated analyser is a medical laboratory instrument designed to measure different chemicals and other characteristics in a number of biological samples quickly, with minimal human assistance....
s count blood cells, a very high MCHC (greater than about 370 g/L) may indicate the blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
is from someone with a cold agglutinin
Cold agglutinin
Cold agglutinin disease is an autoimmune disease characterized by the presence of high concentrations of circulating antibodies, usually IgM, directed against red blood cells...
. 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 anemia.
There are 4 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 agglutininCold agglutininCold agglutinin disease is an autoimmune disease characterized by the presence of high concentrations of circulating antibodies, usually IgM, directed against red blood cells...
- 3. Saline replacement - Replace plasma with same amount of SalineSalineSaline may refer to:* Salinity, the salt content of a solution** Saline water, water containing significant concentration of salts* Soil salinity, salt content of soil* Saline , a liquid with salt content to match the human body...
to exclude interference eg. Lipemia and Auto-immune antibodies - if the MCHC corrects, report corrected results and comment on Lipemia - 4. Check the slide for Spherocytosis (eg. in Hereditary spherocytosisHereditary spherocytosisHereditary spherocytosis is a genetically-transmitted form of spherocytosis, an auto-hemolytic anemia characterized by the production of red blood cells that are sphere-shaped rather than bi-concave disk shaped , and therefore more prone to hemolysis.-Symptoms:As in non-hereditary spherocytosis,...
, among other causes)
See also
- Red blood cell indicesRed blood cell indicesRed blood cell indices are blood tests that provide information about the hemoglobin content and size of red blood cells. Abnormal values indicate the presence of anemia and which type of anemia it is.- Mean corpuscular volume :...
- Mean corpuscular volumeMean corpuscular volumeThe mean corpuscular volume, or "mean cell volume" , is a measure of the average red blood cell size that is reported as part of a standard complete blood count....
- Mean corpuscular hemoglobinMean corpuscular hemoglobinThe mean corpuscular hemoglobin, or "mean cell hemoglobin" , is the average mass of hemoglobin per red blood cell in a sample of blood. It is reported as part of a standard complete blood count...
- Mean corpuscular volume