White Blood Cell Differential: About Your Child's Test

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What is it?

A white blood cell differential counts the different types of white blood cells in a blood sample. There are five main kinds of white blood cells. The numbers of each type of white blood cell give information about your child's immune system.

Why is this test done?

The test helps your doctor decide if your child has an infection or serious illness. It can also help measure certain allergic reactions. It can help your doctor see how well any treatment for cancer is working.

How do you prepare for the test?

In general, you don't need to prepare before your child has this test. Your child's doctor may give you some specific instructions.

How is the test done?

A health professional uses a needle to take a blood sample, usually from the arm.

Your doctor may order a blood smear test to be done at the same time. In this test, a drop of blood is smeared on a slide and stained with a special dye. The slide is looked at under a microscope. The number, size, and shape of red blood cells, white blood cells, and platelets are recorded. Blood cells with different shapes or sizes can help diagnose many blood diseases, such as leukemia, malaria, and sickle cell disease.

How long does the test take?

This test will take a few minutes.

Follow-up care is a key part of your child's treatment and safety. Be sure to make and go to all appointments, and call your doctor if your child is having problems. Ask your doctor when you can expect to have your child's test results.

Where can you learn more?

Go to https://www.healthwise.net/patientEd

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The Health Encyclopedia contains general health information. Not all treatments or services described are covered benefits for Kaiser Permanente members or offered as services by Kaiser Permanente. For a list of covered benefits, please refer to your Evidence of Coverage or Summary Plan Description. For recommended treatments, please consult with your health care provider.