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Complete Blood Count (CBC) Test and Sickle Cell Disease 

A complete blood count (CBC) test can help the care team monitor your child’s sickle cell disease. This test can help the care team find out if treatments are working.

The complete blood count test measures levels of:

  • Red blood cells
  • Hemoglobin
  • Reticulocytes
  • White blood cells
  • Neutrophils
  • Platelets

Abnormal blood cells and sickle cell disease

Children with sickle cell disease have abnormal red blood cells. Other blood cells may also be abnormal. That is why it is vital to monitor blood cells regularly.

Blood cells have important jobs such as fighting infection and carrying oxygen to tissues and organs.

The body has 3 main types of blood cells:

  • Red blood cells
  • White blood cells
  • Platelets
Normal red blood cell and sickled red blood cell

In sickle cell disease, abnormal hemoglobin causes red blood cells to become banana-shaped.

Hemoglobin levels

Red blood cells have a protein called hemoglobin. Red blood cells in the blood travel to the lungs. Hemoglobin picks up oxygen as the cells travel through the lungs. The red blood cells deliver this oxygen to the body’s tissues and organs.

People with sickle cell disease have an abnormal kind of hemoglobin called sickle hemoglobin or hemoglobin S. There are several kinds of abnormal hemoglobin S.

Abnormal hemoglobin S makes red blood cells:

  • Not last as long as they should
  • Form a banana shape
  • Become sticky, stiff, and rigid
  • Clog the small blood vessels in the body

Your child’s hemoglobin levels depend on their type of sickle cell disease and their treatment. 

It is important to know your child’s hemoglobin levels. The numbers will change due to the disease, treatments, and other factors.  

The care team can explain what your child’s hemoglobin levels mean.

Reticulocyte count

A reticulocyte is a young red blood cell made in the bone marrow. The reticulocyte count measures the number of reticulocytes in the blood.

The number is usually quite low. Most reticulocytes stay in the bone marrow until they develop into red blood cells.

A child with sickle cell disease may have a higher reticulocyte count than normal. The number of reticulocytes is different for each person with sickle cell disease. If the reticulocyte count drops very low, your child is making fewer red blood cells. It can be dangerous to have too few.

Your child’s care team can explain what the results mean based on your child’s situation.

White blood cell count

White blood cells help your child’s body fight infection. A low white blood cell count puts your child at risk for infection. It is also harder for a child with a low blood cell count to get over an infection.

A child with sickle cell disease may have a white blood cell count that is higher than normal. But illness and some medicines can make the white blood cell count go up or down for a short time.

The care team can explain what your child’s results mean.

Absolute neutrophil count (ANC)

A neutrophil is type of white blood cell that kills germs. A child who does not make enough neutrophils has a condition called neutropenia. Your child may get more infections and recover slower.

Some children with sickle cell disease take hydroxyurea, which can cause mild neutropenia. Your child’s care team may order an absolute neutrophil count (ANC) test to track your child’s neutrophil levels. The ANC shows how well your child’s body might fight infections.

Some patients have a normal number of neutrophils. But they might not work properly. These people may need other tests.

The care team can explain what your child’s results mean.

Platelet count

Platelets are blood cells that make the body stop bleeding. They help form a blood clot. If your child has a low platelet count, they may bruise or bleed more easily. Sickle cell disease does not usually cause low platelet levels.

Your child’s care team can explain what their individual results mean.

Key points about CBC tests

  • The complete blood count test (CBC) measures levels of red blood cells, hemoglobin, reticulocytes, white blood cells, neutrophils, and platelets.
  • People with sickle cell disease have abnormal hemoglobin that causes red blood cells to be banana-shaped, sticky, and stiff.
  • Your care team uses CBC results to monitor your child’s sickle cell disease and how they respond to treatment.


Reviewed: October 2022