White Blood Cell Count

A white blood cell (WBC) count, also known as a leukocyte count, is a medical test that measures the number of white blood cells in a person's blood.

Purpose

The purpose of a WBC count is to:

• Help diagnose infections, inflammatory diseases, and other conditions that affect the immune system
• Monitor the effectiveness of treatment for certain conditions, such as leukemia or lymphoma
• Check for signs of infection in people with weakened immune systems, such as those with HIV/AIDS or undergoing chemotherapy

Procedure

A WBC count is typically performed using a blood sample collected from a vein in the arm. The procedure involves:

• Inserting a needle into a vein to collect a small amount of blood
• Placing the blood sample into a tube that contains an anticoagulant to prevent clotting
• Sending the blood sample to a laboratory for analysis

Types of White Blood Cells

There are five main types of white blood cells, each with different functions:

• Neutrophils: help fight bacterial infections
• Lymphocytes: play a key role in the immune response and help fight viral infections
• Monocytes: mature into macrophages, which help clean up debris and foreign substances
• Eosinophils: involved in allergic reactions and fighting parasitic infections
• Basophils: play a role in inflammatory responses and allergic reactions

Normal Values

The normal range for a WBC count varies depending on the laboratory and the individual's age, but generally falls within the following ranges:

• Adults: 4,500-11,000 cells per microliter (µL)
• Children: 5,000-15,000 cells/µL
• Infants: 6,000-17,000 cells/µL

Abnormal Results

An abnormal WBC count can indicate a range of conditions, including:

• Infections, such as pneumonia or sepsis
• Inflammatory diseases, such as rheumatoid arthritis or lupus
• Leukemia or lymphoma
• Immune system disorders, such as HIV/AIDS

Risks and Limitations

The WBC count is a relatively safe and simple test, but there are some risks and limitations to consider:

• Bleeding or bruising at the needle site
• Infection at the needle site
• False-negative results if the blood sample is not handled properly
• False-positive results if the individual has a condition that affects the WBC count, such as a recent vaccination or medication use