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White Blood Cell Differential: About This Test

What is it?

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

Why is this test done?

The test helps to measure how the body is responding to different types of infections. It can also help measure certain allergic reactions. It can sometimes be helpful in finding the stage of leukemia or how the body is responding to chemotherapy.

How can you prepare for the test?

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

What happens during the test?

A health professional takes a sample of your blood.

What else should you know about the test?

  • Your results will include an explanation of what a "normal" result is. This is called a "reference range." It is just a guide. Your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed may still be normal for you.
  • 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.

What happens after the test?

  • You will probably be able to go home right away.
  • You can go back to your usual activities right away.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse call line if you are having problems. It's also a good idea to keep a list of the medicines you take. Ask your doctor when you can expect to have your test results.

Where can you learn more?

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