What Are Red Blood Cell Indices?
Red blood cell (RBC) indices are part of a routine blood test called
the complete blood count (CBC). The CBC is used to measure your general health.
It measures the quantity and physical characteristics of different types of
cells found in your blood.
Blood consists of RBCs, white blood cells, and platelets that are
suspended in your plasma. Platelets are cells that enable clot formation. RBCs
contain hemoglobin, which carries oxygen throughout your body. An RBC is pale
red and gets its color from hemoglobin. It’s shaped like a doughnut, but it has
a thinner area in the middle instead of a hole. Your RBCs are normally all the
same color, size, and shape. However, certain conditions can cause variations
that impair their ability to function properly.
The RBC indices measure the size, shape, and physical
characteristics of the RBCs. Your doctor can use RBC indices to help diagnose
the cause of anemia. Anemia is a common blood disorder in which you have too
few red blood cells.
Why Do I Need to Have RBC Indices?
Your RBC indices and RBC count are used to diagnose different
types of a condition called anemia. You have some form of anemia if you have a
low RBC count or abnormal RBC indices.
Anemia is a condition in which the number of RBCs or the amount
of hemoglobin in your blood falls below normal levels. This deprives tissues
throughout your body of needed levels of oxygen. You may feel tired or have
other symptoms if your body doesn’t get all the oxygen it needs.
Anemia can occur if:
- too few RBCs are created, which is called
- RBCs are destroyed prematurely, which is called
- a significant blood loss occurs
Anemia has many different causes. It can be inherited, which
means it’s due to a genetic condition passed down from parents to children
through their genes. Anemia can also develop sometime during your life, which
means it’s acquired. Anemia can be acute or chronic.
The possible causes of anemia include:
- diets lacking in iron, vitamin B-12, folate, or
- chronic diseases like cancer, diabetes,
inflammatory bowel disease, kidney disease, or thyroiditis, which is an
inflammation of your thyroid gland
- chronic infections like HIV or tuberculosis
- significant blood loss
- diseases affecting your bone marrow, such as
leukemia, lymphoma, or multiple myeloma
- lead poisoning
- certain genetic diseases, such as thalassemia,
which is an inherited form of anemia, or sickle cell disease, which occurs when
your RBCs can’t carry oxygen well because they’re sickle-shaped
Iron deficiency anemia is the most common kind of anemia.
The symptoms of anemia can be very mild at first. Many people
aren’t even aware that they’re anemic. The most common early symptoms of anemia
- lack of energy
- pale skin
As the disease progresses, your symptoms may include:
- a feeling of cold or numbness in your hands and
- shortness of breath
- irregular or fast heartbeat
- chest pains
- brittle nails
Most people don’t know they have anemia until they have a CBC,
which is a routine test. The CBC is a broad test that measures the number of
all RBCs, WBCs, and platelets in a sample of blood. If you’re found to have
anemia, the RBC and the RBC indices can help to determine what’s causing your anemia.
What Happens During RBC Indices?
The test for RBC indices involves taking a small sample of blood.
You don’t need to prepare for it. The following steps describe what happens:
- If the blood is taken from a vein inside your
elbow, a healthcare provider will first clean the test area with an antiseptic
and wrap an elastic band around your upper arm to make the vein swell.
- A needle is gently inserted, and blood flows
into a tube.
- When the tube is filled, the healthcare provider
removes the elastic band and then removes the needle.
- A bandage may be placed over the area where the
needle was inserted.
- The sample is then sent to a laboratory for
What Are the Different Parts of RBC Indices?
The RBC indices has three parts:
- mean corpuscular volume (MCV), which is the
average red blood cell size
- mean corpuscular hemoglobin (MCH), which is the
amount of hemoglobin per red blood cell
- mean corpuscular hemoglobin concentration (MCHC),
which is the amount of hemoglobin relative to the size of the cell or
hemoglobin concentration per red blood cell
According to the American
Association for Clinical Chemistry, normal values for RBC indices are:
- The MCV should be 80 to 96 femtoliters.
- The MCH should be 27 to 33 picograms per cell.
- The MCHC should be 33.4 to 35.5 grams per deciliter.
Normal ranges may vary slightly from lab to lab.
What Do the Results Mean?
The RBC indices can help your doctor determine the cause if your
doctor thinks you have anemia. The MCV is the most useful value in the RBC
indices to help determine the type of anemia you may have.
Your doctor will see if your MCV is low, normal, or high to help
determine what is causing your anemia.
The MCV is higher than normal when red blood cells are larger
than normal. This is called macrocytic anemia.
Macrocytic anemia can be caused by:
- B-12 deficiency
- folate deficiency
The MCV will be lower than normal when red blood cells are too
small. This condition is called microcytic anemia.
Microcytic anemia may be caused by:
- iron deficiency, which can be caused by poor
dietary intake of iron, menstrual bleeding, or gastrointestinal bleeding
- lead poisoning
- chronic diseases
If you have a normal MCV, it means that your red blood cells are
normal in size. You can have a normal MCV and still be anemic when there are
too few red blood cells or when other RBC indices are abnormal. This is called
Normocytic anemia occurs when the red blood cells are normal in
size and hemoglobin content, but there are too few of them. This can be caused
- a sudden and significant blood loss
- a prosthetic heart valve
- a tumor
- a chronic disease, such as a kidney disorder or
- aplastic anemia
- a blood infection or sepsis
After the Test
Your doctor may also perform other tests to help them make a
diagnosis. Treatment for any anemia depends on what’s causing it. For example,
if your anemia is caused by a lack of iron, your doctor may advise you to take
iron supplements or change your diet to include more foods that are rich in
iron. If you have an underlying disease that’s causing anemia, treatment for
that disease can often also treat the anemia.
Talk to your doctor if you’re experiencing any of the symptoms of
anemia or if you have any concerns about the results of your CBC or RBC