What Is Mean Corpuscular Hemoglobin Concentration (MCHC)?

What to expect when undergoing this test

Mean corpuscular hemoglobin concentration (MCHC) is lab value found on a complete blood count (CBC) that describes the average concentration of hemoglobin in a given volume of red blood cells. Hemoglobin is what gives red blood cells their color, and therefore a higher concentration of hemoglobin with high MCHC makes the cells appear darker (hyperchromic) and a low concentration with low MCHC makes them appear lighter (hypochromic).

The value of MCHC is helpful in diagnosing anemia, but is used along with the red blood cell count (RBC) and other red blood cell indices such as MCV and RDW.

In addition to its role in evaluating blood disorders, MCHC may be helpful even when the red blood cell count is normal (in a person who doesn't have anemia), such as in helping doctors predict the prognosis after a heart attack and more.

Purpose of Test

Since the mean corpuscular hemoglobin concentration (MCHC) is done as part of a complete blood count (CBC), the test is done any time a CBC is ordered. This may include routine health screenings or during the diagnosis, treatment, and follow-up of a wide range of medical conditions.

Reasons a doctor may specifically look at the MCHC include:

  • when symptoms of anemia are present such as fatigue, pale skin, or lightheadedness
  • when looking for the different causes of anemia (when a person's red blood cell count (RBC) and/or hemoglobin levels are low)
  • \when considering the prognosis of medical conditions such as heart attacks or lung cancers

Measuring MCHC

MCHC is calculated by multiplying the hemoglobin level times ten and then dividing by the hematocrit level. The number is recorded in grams per liter.

  • MCHC = Hb x 10 / hematocrit

MCHC may also be calculated by dividing the mean corpuscular hemoglobin by the mean corpuscular volume:

  • MCHC = MCH / MCV

Meaning of MCHC

The mean corpuscular hemoglobin concentration is a measure of the concentration of hemoglobin in cells.

Since hemoglobin is the molecule to which oxygen attaches, MCHC is a measure of the average oxygen carrying capacity of the red blood cells circulating in the body.

A low MCHC (hypochromia) means that there is a lower concentration of hemoglobin within a given volume of red blood cells, and hence, a reduced capacity to carry oxygen to the tissues. A normal (normochromia) or high MCHC (hyperchromia) means that the oxygen-carrying capacity of the red blood cells is normal, but it may still be deficient if not enough red blood cells are present.

Limitations

There are several limitations that can affect the accuracy of the MCHC reading including.

Post-Transfusion

Since blood drawn after a blood transfusion will be a mixture of donated cells plus a person's normal red blood cells, the MCHC won't give accurate information about the original red blood cells present.

Combined Anemia

If a person has two different types of anemia that lead to different MCHC levels, the reading won't be as helpful in diagnosing the type of anemia. For example, the MCHC may be normal if a person has a combination of iron deficiency anemia (which causes a low MCHC) and spherocytosis (which tends to cause a high MCHC).

Conditions that Give Inaccurate Hemoglobin or Hematocrit levels

Since MCHC is calculated using the hemoglobin and hematocrit, anything that falsely increases or decreases these numbers will give a false MCHC result. For example, hyperlipidemia (an increased level of cholesterol or triglycerides), hyperbilirubinemia (elevated bilirubin levels in the blood as with liver disease), and autoagglutination will cause the hematocrit level to be falsely high and the hemoglobin levels to be falsely low.

With hemolysis (breakdown of red blood cells), free hemoglobin in the plasma that is left over from the broken red blood cells will also cause an abnormal result—the MCHC will be falsely increased.

Similar Tests

The mean corpuscular hemoglobin (MCH) test measures the average mass of hemoglobin per red blood cell. While the name sounds similar to MCHC, it actually provides information that is more similar to the MCV (mean corpuscular volume or MCV affects the amount of hemoglobin in the cell).

Many physicians consider MCH to be the least helpful of the red blood cell indices and look primarily at the MCV in this setting. When compared with MCH, MCHC is a much better test for detecting hypochromia.

Complementary Tests

In addition to MCHC, a complete blood count provides information including the total number of red blood cells (RBCs), white blood cells (WBCs), and platelets as well as other red blood cell indices:

  • Mean corpuscular volume (MCV): MCV is a measure of the average size of the red blood cells
  • Red cell distribution width (RDW): RDW is a number that reflects the variation in sizes of the red blood cells
  • Mean corpuscular hemoglobin (MCH): MCH is the average mass of hemoglobin per red blood cell

In addition, other tests may be done such as a peripheral blood smear for morphology and reticulocyte count, and when indicated, iron studies, vitamin B12 levels, and more may be needed to further clarify information found on the CBC.

Risks and Contraindications

There are a few potential risks to having a CBC performed, including a small risk of bleeding, bruising, and infection.

Before the Test

There are no dietary or activity restrictions prior to having a CBC. It's important to bring your insurance card to your appointment and to make sure your doctor has access to prior CBCs you have had for comparison.

During the Test

The test can be conducted in many hospitals and clinics. Prior to drawing your blood, a lab technician will cleanse the area (usually a vein in the arm) with an antiseptic and a tourniquet is applied to better visualize the vein. If you have a chemotherapy port, blood can be drawn directly from the port.

The technician will then insert the needle into a vein. You may feel a sharp poke when the needle enters, and some pressure as it remains in place. Some people may feel lightheaded or faint with the needle stick. Make sure to let the technician know if you are feeling lightheaded. After obtaining the sample, the technician will remove the needle and ask you to hold pressure over the site.

When the bleeding has stopped, a bandage will be applied or gauze wrapped around your arm to keep the area clean and to reduce the chance of further bleeding.

After the Test

When the test is done, you will be able to return home and resume your regular activities. Potential side effects include:

  • pain from the needle stick, especially if many attempts are made
  • difficulty obtaining a specimen from a blood draw (such as in people whose veins are difficult to access due to chemotherapy)
  • bleeding (bleeding can take longer to stop in people who are on blood thinners or have a bleeding disorder)
  • hematoma or a large bruise may form and can be uncomfortable, but it is very uncommon
  • infection (when the skin is penetrated, there is a small risk of bacteria being introduced into the body)

Interpreting Results

If your clinic has a lab on site, you may receive your results shortly after they are drawn. Other times, your doctor may call you to give you your results. It's important to be your own advocate and ask for the actual numbers (for example, your MCHC) rather than whether your CBC is simply normal or not.

Reference Range

The "normal" range for MCHC can vary somewhat between different labs but is usually between 32 and 36. Some labs have a smaller range of normal, for example, between 33.4 and 35.5.

The MCHC is calculated from hemoglobin and hematocrit, so anything that interferes with these numbers will make the MCHC inaccurate. Results will also be inaccurate after a transfusion (they will reflect the characteristics of the transfused cells combined with a person's own cells).

Normal MCHC

MCHC may be normal with many types of anemia (normochromic anemias) such as:

  • blood loss anemia
  • anemia due to kidney disease
  • mixed anemias
  • bone marrow failure
  • hemolytic anemias (many types)

Causes of a Low MCHC

When the MCHC is low (unless the result is inaccurate due to one of the limitations noted earlier), it means that the red blood cells do not have enough hemoglobin. Possible causes include:

  • Iron deficiency (with or without anemia)
  • Lead poisoning
  • Thalassemias (beta thalassemia, alpha thalassemia, and thalassemia intermedia)
  • Sideroblastic anemia
  • Anemia of chronic disease

A low MCHC without anemia is associated with poor outcomes for people in intensive care. It may also indicate iron deficiency before anemia develops.

Causes of a High MCHC

A high MCHC means that hemoglobin is more concentrated than usual and may occur in a few ways. For instance, hemoglobin becomes more concentrated with red blood cells break down. MCHC is often increased in people who smoke. MCHC may also be falsely increased due to cold agglutinin disease

Potential causes of a high MCHC with anemia include:

  • Autoimmune hemolytic anemia (due to medications, autoimmune conditions, and more)
  • Hereditary spherocytosis
  • Severe burns
  • Liver disease
  • Hyperthyroidism
  • Sickle cell disease (homozygous)
  • Hemoglobin C disease

Using MCHC with Other Red Blood Cell Indices

MCHC results are most helpful when used in conjunction with other red blood cell indices, especially mean corpuscular volume (MCV).

For instance, low MCHC and low MCV could indicate iron deficiency anemia, thalassemia, sideroblastic anemia, or lead poisoning. A high MCHC and low MCV could indicate spherocytosis or sickle cell disease.

Normal MCHC and high MCV could mean a vitamin B12 or folate deficiency or liver disease.

Other Tests That May Be Helpful in Classifying Anemias

In addition to blood counts and red blood cell indices, additional tests that may be needed include:

  • Peripheral Blood Smear for Morphology: A peripheral smear involves looking at the blood sample under the microscope. This allows the technician to directly visualize other changes in the red blood cells that may be associated with anemia such as target cells, nucleated red blood cells, and more.
  • Iron Studies: Serum iron and iron-binding capacity and/or ferritin levels can give valuable information on iron stores and can help discriminate iron deficiency from other anemias with a low MCHC.
  • Vitamin B12 Level: Vitamin B12 levels are helpful in looking for pernicious anemia.
  • Bone Marrow Aspiration and/or Biopsy: In some cases, a bone marrow study may be needed to assess the appearance of blood cells in the bone marrow and iron stores.

MCHC in Medical Conditions Other Than Anemia

Historically, red blood cell indices were used primarily in characterizing anemias, but these numbers may provide important information even when there are no signs of anemia.

One study found that MCHC was useful in estimating the prognosis after myocardial infarction. In this setting, MCHC appears to be an independent measure of both short term and long term prognosis after a heart attack.

A low MCHC may predict survival with lung cancer as well. In people undergoing surgery for lung cancer, those who were not anemic but had a lower MCHC had a poorer survival rate (by a factor of 42 percent) than those with a normal MCHC.

In addition to physical conditions, MCHC may play a role in the assessment of mental health as well. One study found that MCHC was helpful in predicting the risk of future depression in women.

A Word From Verywell

Mean corpuscular hemoglobin concentration (MCHC) is most meaningful when combined with other results on a CBC and can be helpful in discriminating causes of anemia as well as predicting prognosis in those without anemia. When using these results, however, it's very important to be aware of the limitations as well as the potential of error and to use any findings only after they are repeated and supported by other studies.

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Article Sources
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