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May Article 2016: Blood Tests for Children with Cancer

May 4, 2016


Blood test results of children being treated for cancer often fluctuate wildly. The number of white blood cells can go down to zero or be above normal. Levels of red blood cells and/or platelets may go down periodically during treatment, necessitating transfusions. Absolute neutrophil counts (ANC) are closely watched, as they give the oncologist an idea of the child’s ability to fight infections; ANCs range from zero into the thousands.

Pediatric oncologists consider all of the blood test results to get the total picture of a child’s reaction to chemotherapy, radiation, or illness. Trends are more important than any single value. The section below describes some of the most common blood tests given to children with cancer.

Common Blood Tests

Article-BloodTests-rbc2Red Blood Cell Count (RBC)

Red blood cells are produced by the bone marrow continuously in healthy children and adults. These cells contain hemoglobin, which carries oxygen throughout the body. When a child is on chemotherapy, the bone marrow does not make many red cells. When the RBC count is low, less oxygen is carried in the blood, so your child will have less energy.

White Blood Cell Count (WBC)

The total WBC indicates the body’s ability to fight infection. Some treatments for childhood cancer kill healthy white cells or decrease the ability of the bone marrow to make new ones.

White Blood Cell Differential

When a child has blood drawn for a complete blood count (CBC), one section of the lab report will state the total WBC and a “differential,” meaning that each type of white blood cell will be listed as a percentage of the total. For example, if the total WBC count is 1,500 mm3, the differential might appear as in the following table:

Article-BloodTests-wbctable

Absolute Neutrophil Count (ANC)

The ANC (also called the absolute granulocyte count or AGC) is a measure of the body’s ability to fight infection. Generally, an ANC above 1,000 means the child’s infection-fighting ability is near normal.

To calculate the ANC, add the percentages of neutrophils (both segmented and band) and multiply by the total WBC. Using the example above, the ANC is 49 percent + 1 percent = 50 percent, and 50 percent of 1,500 (.50 x 1,500) = 750, so the ANC is 750.

Article-BloodTests-plateletPlatelet Count

Platelets are needed to repair the body and stop bleeding by forming clots. Because platelets are produced by bone marrow, platelet counts often decrease when a child or teen is on chemotherapy. Signs of low platelet counts are bruises and bleeding from the gums or nose. Platelet transfusions are sometimes given when the platelet count is lower than 20,000 or when there is bleeding.

Alanine Aminotransferase (ALT)

When doctors talk about liver functions, they are usually referring to blood tests that measure liver damage. If chemotherapy is causing liver damage, the liver cells release an enzyme called ALT into the blood. ALT levels can go up into the hundreds, or even thousands, in some children on chemotherapy. Each institution and protocol has different points at which chemotherapy drug dosages are decreased or stopped to allow the child’s liver to recover. ALT is also called serum glutamic pyruvic transaminase (SGPT).

Aspartate Aminotransferase (AST)

AST is an enzyme present in high concentrations in tissues with high metabolic activity, such as the liver. Severely damaged or killed cells release AST into the blood. The amount of AST in the blood is directly related to the amount of tissue damage. Therefore, if your child’s liver is being damaged by chemotherapy, the AST count can rise into the thousands. Viral infections or reactions to an anesthetic can also cause an elevated AST. AST is also called serum glutamic oxaloacetic transaminase (SGOT).

Bilirubin

The liver converts hemoglobin released from damaged red cells into bilirubin. The liver then removes bilirubin from the blood and excretes it into bile, which is a fluid released into the small intestine to aid digestion. If too much bilirubin is present in the body, it causes a yellow color in the skin and whites of the eyes that is called jaundice.

Creatinine

Creatinine is a breakdown product of protein metabolism found in the urine and the blood. In children with cancer, creatinine is sometimes measured to assess kidney function.

Potassium

Potassium is important for the proper functioning of the nerves and muscles, particularly the heartbeat. Too much or too little potassium increases the chance of irregular heartbeats.

Article-BloodTests-healthcheckCalcium and Magnesium

Calcium and magnesium are minerals that can be compared to the spark plugs in your car––they spark the chemical reactions in your body needed to make it function properly. Calcium and magnesium also help to develop and maintain the strength of bones. In addition, magnesium is necessary for the development of muscle and for nerve conduction throughout the body. Many chemotherapy drugs given to children with cancer decrease the calcium and magnesium levels in the blood.

Your Child’s Pattern

Each child develops a unique pattern of blood counts during treatment, and some parents like to track the changes. You can put lab sheets in a binder or enter blood test results into a computer program that shows trends over time. Doctors consider all of the laboratory results before deciding on a course of action. They should be willing to explain their plan so you can better understand what is happening and worry less.

If your child is participating in a clinical trial and you have obtained the entire clinical trial protocol, it will contain a section that clearly outlines the actions that should be taken by the pediatric oncologist if certain changes in blood counts occur. For example, most protocols list each drug and when the dosage should be modified. The following is an example from a protocol for the drug vincristine.

  • Vincristine
    • 1.5 mg/m2 (2 mg maximum) IV push weekly x 4 doses days 0, 7, 14, 21.
  • Seizures
    • Hold one dose, then reinstitute.
  • Severe foot drop, paresis, or ilius
    • Hold dose(s): when symptoms abate, resume at 1.0 mg/m2; escalate to full dose as tolerated.
  • Jaw pain
    • Treat with analgesics; do not modify vincristine dose.
  • Bilirubin
    • Withhold if total bilirubin is >1.9 mg/dL.
    • Administer 1/2 dose if total bilirubin is 1.5–1.9 mg/ dL.

 

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© 2016 Nancy Keene
Permission is required from the publisher (info@childhoodcancerguides.org) to use the content in this article for any purpose. This material was excerpted from Childhood Cancer: A Practical Guide to Your Future, 3rd ed. (2016)

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