White blood cell differential

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.

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.

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.

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