How to Read WBC Differential Numbers

White blood cells, also called leukocytes, are part of the immune system and defend the body against infections and foreign elements. There are five major types of white blood cells: basophils, eosinophils, lymphocytes, monocytes and neutrophils. A white blood cell differential indicates the percentage of each type of cell in a tested blood sample. The differential helps in determining the body's ability to respond to and eliminate infection. It also detects the severity of infections and allergic reactions.

Instructions

• 1

  Compare the neutrophil differential to the reference range. A normal range is 40 percent to 60 percent. Neutrophils are the body's main defenders against antigens and infections. If the neutrophil value is significantly higher than the normal range, it could indicate an infection or inflammatory disease. Bone marrow disorders also lead to severe elevations in neutrophil levels. A lower-than-normal value indicates a threat to the immune system.

• 2

  Review the eosinophil differential. Eosinophils fight against parasites and most other infections. One percent to 4 percent is considered a normal range. Elevated eosinophil levels can result from allergic reactions or parasitic infections. Low levels are usually not an issue.

• 3

  Compare the basophil differential. Low levels of basophils are considered typical, with the normal range being 0.5 percent to 1 percent. An increase in basophils can occur because of leukemia, chronic inflammation, a hypersensitivity reaction to food, or radiation therapy. Basophil counts are used to identify the body’s resistance to allergies.

• 4

  Compare the lymphocyte differential. The normal range is 20 percent to 40 percent. These white blood cells defend the body against viral infections. High levels of lymphocytes may be caused by viral infections. Decreased lymphocyte levels can indicate immune system diseases, such as lupus, and the later stages of HIV infection.

• 5

  Review the monocyte differential. Monocytes act as the body's second line of defense. The normal range is 2 percent to 8 percent. Results higher than 10 percent may indicate tissue malfunction. Monocyte levels can decline because of bone marrow injury and some forms of leukemia.