What are blood counts?
Blood is made up of cells in a liquid called plasma. Blood cells are made in the bone marrow (the soft center of the bones). Then they are released into the body to do their jobs. The body has 3 main types of blood cells: red blood cells, white blood cells, and platelets. Sickle cell disease mainly affects the red blood cells, but can sometimes affect other blood cells. Medicines for sickle cell disease can also affect blood cells.
If your child has sickle cell disease, counting and studying blood cells can tell the St. Jude staff about your child’s disease and how to treat it. A complete blood count (CBC) is a test that tells your child’s doctor about all 3 types of blood cells: red blood cells, platelets, and white blood cells.
Red blood cells
The main purpose of red blood cells is to deliver oxygen to the body. The part of the blood that carries oxygen is called hemoglobin. People with sickle cell disease have abnormal hemoglobin, called sickle hemoglobin or hemoglobin S. If your child has sickle cell disease, her red blood cells do not last as long because the sickle hemoglobin damages them. This means your child has fewer red blood cells than normal, a condition called anemia. People with normal hemoglobin usually have a hemoglobin level around 12 g/dL. People with sickle cell disease have lower hemoglobin levels, usually between 6–11 g/dL. The exact level may be different depending on the type of sickle cell disease and the person. It is important to know your child’s usual hemoglobin level. Blood tests done over a period of time will tell the doctor what is normal for your child.
A reticulocyte is a young red blood cell that is forming in the bone marrow. Normally, reticulocytes stay in the bone marrow until they develop into red blood cells and enter the blood. The reticulocyte count is a test that measures the number of reticulocytes in the blood. For most people, the number is very low because most reticulocytes stay in the bone marrow. If your child has sickle cell disease, she may have a higher reticulocyte count. This is because your child’s body has to make more red blood cells due to anemia. A normal amount of reticulocytes in the blood is between 0.45–1.8 percent. If your child has sickle cell disease, she may have a reticulocyte count of 2–3 percent or more. The number of reticulocytes is different for each person with sickle cell disease. If your child’s reticulocyte count drops very much, it might mean her body is making fewer red blood cells. This could be dangerous. The St. Jude staff will test your child’s reticulocyte count at each clinic visit.
White blood cells
White blood cells help the body fight infection. A normal white blood cell count is 5,000–10,000/mm3. When the white blood cell count is low, it is easier to get an infection and harder to get over it. If your child has sickle cell disease, her white blood cell count will usually be normal or higher than normal. However, illness and some medicines can make the white blood cell count go up or down for a short time.
A neutrophil is a type of white blood cell that kills bacteria. Neutrophils help prevent infection. If your child does not have enough neutrophils, this is called neutropenia. Children taking hydroxyurea for sickle cell disease often have mild neutropenia. If your child is taking hydroxyurea, the St. Jude staff will keep track of your child’s neutrophil count.
The doctor will use a measurement called the Absolute Neutrophil Count (ANC) to keep track of your child’s neutrophils. The ANC shows how well the body can fight infections, especially bacterial infections.
Platelets are blood cells that help stop bleeding by making the blood clot. A normal platelet count is 150,000 to 400,000/mm3. If your child has a low platelet count, she may bruise or bleed more easily. Normally, sickle cell disease does not cause low platelet levels.
Keeping track of your child’s blood counts
If your child has sickle cell disease, the St. Jude staff will keep track of her blood counts. Your child will usually have a complete blood count (CBC) and reticulocyte count at each clinic visit. The doctor will tell you if your child needs more blood tests. Keeping track of your child’s blood counts is an important part of treatment. The St. Jude staff will review the test results with you and give you a copy each time your child sees the doctor. You should keep these results with your child’s medical records.
If you have questions about your child’s blood counts or what they mean, ask the doctor or nurse. If you are outside the hospital, refer to your Important Phone Number Card. You may also call the St. Jude operator at (901) 595-3300 or toll-free 1-866-2STJUDE (1-866-278-5833) and ask for your child’s nurse case manager.
This document is not intended to take the place of the care and attention of your personal physician or other professional medical services. Our aim is to promote active participation in your care and treatment by providing information and education. Questions about individual health concerns or specific treatment options should be discussed with your physician.
St. Jude complies with health care-related federal civil rights laws and does not discriminate on the basis of race, color, national origin, age, disability, or sex.
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