Mean Corpuscular Hemoglobin (MCH) and Mean Corpuscular Hemoglobin Concentration (MCHC)
- Author: Brian Yang Merritt, MD; Chief Editor: Thomas M Wheeler, MD more...
The reference ranges for mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration are as follows:
Normal values may vary depending on the individual laboratory.
Both mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) reflect the average hemoglobin content of red blood cells in slightly different ways (see "Description" in Background). Although MCH expresses the average content (mass, weight) of hemoglobin per red cell, MCHC expresses the average weight of hemoglobin per unit volume of red cell (see also "Understanding MCH and MCHC Using a River Tubing Analogy" in Background).
MCH, MCHC, and MCV are parts of red cell indices (parameters reflecting size and hemoglobin content of red cells) that have traditionally been used to aid in the differential diagnosis of anemia. Although MCH can be used to determine if an anemia is hypo-, normo-, or hyperchromic, the mean corpuscular volume (MCV) has to be considered along with the MCH since cell volume (MCV) affects the content of hemoglobin present per cell (MCH), and MCH can decrease or increase in parallel to the MCV. Thus, MCHC in the past has been thought to be a better parameter than MCH to determine hypochromasia.
However, the MCHC, as measured by a multichannel analyzer nowadays, is not affected by plasma trapping, which typically results in slightly increased hematocrit. MCHC is not then decreased when there is hypochromasia. Therefore, MCV together with red cell distribution width (RDW) have become the two most useful parameters in classifying anemias, while MCH and MCHC do not add significant, clinically relevant information.[3, 5] MCH and MCHC, nonetheless, play an important role in laboratory quality control.[2, 3] These parameters allow laboratories to detect potential causes of erroneous results, such as hyperlipidemia or hemolysis (both in vivo and in vitro), so the correct results can be reported.
MCHC, when increased, can be useful clinically as an indicator of increased spherocytes (spherocytosis), as in hereditary spherocytosis or autoimmune hemolytic anemia. It is also increased in homozygous sickle cell or hemoglobin C disease.
Collection and Panels
Specimen: Whole blood, usually collected by venipuncture
Collection: EDTA tube (purple/lavender top; see image below) containing EDTA potassium salt additive as an anticoagulant
Panels: Complete blood count (CBC)
MCH is the content (weight) of hemoglobin (Hb) of the average red cell, or, in other words, a reflection of hemoglobin mass in red cells. It is not measured directly but is calculated from the measured Hb concentration (Hb) and red blood cell count (RBC) as follows:
MCH = Hb (in g/L)/RBC (in millions/µL) or
MCH = [Hb (in g/dL)/RBC (in millions/µL)] x 10
A related value is mean corpuscular hemoglobin concentration (MCHC), which is the average concentration of hemoglobin in a given volume of packed red blood cells, or in other words, the ratio of hemoglobin mass to the volume of red cells. It is also not measured directly but is calculated from the Hb concentration (Hb) and the hematocrit (Hct):
MCHC = Hb (in g/dL)/Hct (%)
As part of a standard CBC, the MCH and MCHC can be used for the evaluation of anemia along with the MCV (see Interpretation).
MCH and MCHC, as well as the MCV, reflect average values and may not adequately reflect RBC changes when mixed RBC populations are present, such as dimorphic RBC populations in sideroblastic anemia or combined iron deficiency anemia (decreased MCV and MCH) and megaloblastic anemia (increased MCV and MCH). An elevated RDW will provide a clue for heterogenous red cell size (anisocytosis) and/or the presence of two red cell populations, and peripheral blood smear review can help confirm the above findings.[2, 5, 7, 8]
MCH can be spuriously increased or decreased when an accurate measurement of Hb concentration and red blood cell count is disturbed, as MCH calculation is derived from these two parameters. For example, hyperlipidemia resulting in plasma turbidity will spuriously increase Hb, hence falsely elevate MCH.
MCHC, as measured by a multichannel analyzer (instrument used nowadays for complete blood count [CBC]), is a stable variable. Therefore, it plays an important role in laboratory quality control.[2, 3] MCHC is spuriously decreased or increased when an accurate measurement of Hb and hematocrit is disturbed, as the MCHC calculation is derived from these two parameters. For example, it can be spuriously increased in autoagglutination and hyperlipidemia due to spuriously low hematocrit and spuriously high Hb, respectively. Truly increased MCHC usually occurs in hereditary spherocytosis (see the second image, below) or in some cases of homozygous sickle cell or hemoglobin C disease.
Understanding MCH and MCHC Using a River Tubing Analogy
To help understand RBC indices, imagine a river tubing scenario. Each RBC is a river tube (doughnut-shaped tube). Many river tubes are in the river, just like many RBCs are in our circulation (a “river of life”). The following hematologic values are then analogous:
RBC count = the number of river tubes per unit volume of river water
Hb concentration = the content (weight) of air in the river tubes per unit volume of river water
Hematocrit = the volume of river tubes per unit volume of river water
MCV = average river tube size (volume)
MCH = average content (weight) of air in each river tube
MCHC = average density of air in each river tube, or average river tube inflation
Certain pathologic conditions such as anemia are associated with a low RBC count (too few river tubes in the river). The images below demonstrate how different types of anemia can be thought of with this analogy.
Vajpayee N, Graham SS, Bem S. Basic Examination of Blood and Bone Marrow. McPherson RA, Pincus MR. Henry’s Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Saunders, an imprint of Elsevier Inc; 2011. Chap 30:509-35.
Perkins SL. Examination of the Blood and Bone Marrow. Greer JP, Foester J, Rodgers GM, et al, eds. Wintrobe’s Clinical Hematology. 12th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009. Chap 1.
Ryan DH. Examination of Blood Cells. Lichtman MA, Kipps TJ, Seligsohn U, et al, eds. Williams Hematology. 8th ed. New York, NY: The McGraw-Hill Companies, Inc; 2010. Chap 2.
Perkins SL, Hussong JW. Red Blood Cells. Jones SL, ed. Clinical Laboratory Pearls. Philadelphia, PA: Lippincott Williams & Wilkins; 2001. 61-96.
Marks PW, Glader B. Approach to Anemia in the Adult and Child. Hoffman F, Benz EJ, Shattil SJ, eds. Hematology: Basic Principles and Practice. 5th ed. Philadelpha, PA: Churchill Livingstone; 2009. Chap 34:439-46.
RBC indices. A.D.A.M. Medical Encyclopedia. Atlanta, GA: A.D.A.M., Inc; 1997-2014. Updated February 8, 2012. Available at http://www.nlm.nih.gov/medlineplus/ency/article/003648.htm. Accessed: February 1, 2014.
Elghetany MT, Banki K. Erythrocytic Disorders. McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Sauders, an imprint of Elsevier Inc; 2011. Chap 32:557-600.
Means RT, Glader B. Disorders of Red Cells. Greer JP, Foester J, Rodgers GM, et al, eds. Wintrobe's Clinical Hematology. 12th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009. Chap 26.