Often abbreviated as WBC.

A laboratory test performed on a sample of a patient’s blood. This is a routine blood test. It determines the number of leukocytes in the blood. Higher than normal counts can indicate the presence of infection or leukemia. A differential is the percentages of different types of white blood cells (neutrophils], esocinophils, basophils, lymphocytes, and monocytes) in a sample of blood. It gives more information about leukocytes and aids in diagnosis of allergic disease, disorders of the immune system, and various forms of leukemia.

To do this test whole blood is mixed with a weak acid solution for the purpose of diluting the blood and gradually declining red blood cells with the liberation of hemoglobin. This diluted blood is then put into a counting chamber called a hemocytomer and the white cells are counted. Then the number of white blood cells per cubic millimeter is calculated.