White Blood Cell Count (WBC)

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Also known as: Leukocyte Count, WBC, White Blood Cell Count, White Blood Cell Count WBC

White Blood Cell Count

A WBC count is a test to measure the number of white blood cells (WBCs) in the blood. WBCs help fight infections. They are also called leukocytes. There are five major types of white blood cells: basophils, eosinophils, lymphocytes (T cells and B cells), monocytes and neutrophils
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The White Blood Cell Count (WBC) test contains 1 test with 1 biomarker.

Brief Description: The White Blood Cell Count (WBC) test, often referred to simply as a "WBC," measures the total number of white blood cells in a sample of blood. White blood cells, also known as leukocytes, are essential components of the immune system, responsible for protecting the body against infections and other foreign invaders. These cells are produced in the bone marrow and are found throughout the bloodstream and the lymphatic system.

Collection Method: Blood Draw

Specimen Type: Whole Blood

Test Preparation: No preparation required

When and Why a White Blood Cell Count Test May Be Ordered

A healthcare provider may order a WBC for several reasons:

  1. Monitor General Health: As part of a routine complete blood count (CBC), to get an overall snapshot of an individual's health.
  2. Diagnose Infections or Disorders: If a patient presents symptoms of an infection, inflammation, or other disorders affecting the blood or immune system.
  3. Monitor Medical Conditions: In individuals with known conditions that may affect the WBC, like leukemia.
  4. Assess Medical Treatment: To see how the body is responding to treatments like chemotherapy.

What the White Blood Cell Count Test Checks For

The WBC test provides a count of the total number of white blood cells in the blood. A differential WBC might further break down this count into the different types of white blood cells, such as neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Each of these has a unique function in the immune response.

Additional Lab Tests Ordered Alongside the White Blood Cell Count Test

When a WBC count is ordered, it's often part of a broader evaluation of the immune system, infection, inflammation, or hematologic conditions. Here are some tests commonly ordered alongside a WBC count:

  1. Complete Blood Count (CBC) with Differential:

    • Purpose: To provide a detailed breakdown of all blood cell types, including red blood cells, white blood cells (with types), and platelets.
    • Why Is It Ordered: To assess overall blood health and to provide more detail on the types of white blood cells (neutrophils, lymphocytes, monocytes, eosinophils, and basophils), which can help identify specific types of infection or hematologic conditions.
  2. Erythrocyte Sedimentation Rate (ESR) and/or C-Reactive Protein (CRP):

    • Purpose: To measure markers of inflammation in the body.
    • Why Is It Ordered: To assess the presence and severity of inflammation, which can accompany infections and various inflammatory or autoimmune conditions.
  3. Prothrombin Time (PT) and Activated Partial Thromboplastin Time (aPTT):

    • Purpose: To assess blood clotting function.
    • Why Is It Ordered: To evaluate the clotting system, especially if there is concern about disorders affecting blood clotting or in the context of certain treatments.
  4. Blood Culture:

    • Purpose: To detect bacteria or fungi in the blood.
    • Why Is It Ordered: In cases of suspected bloodstream infection (sepsis), particularly if there is fever or other signs of systemic infection.
  5. Comprehensive Metabolic Panel - CMP:

    • Purpose: To assess various metabolic functions, including liver and kidney function, electrolytes, and blood sugar levels.
    • Why Is It Ordered: To provide insight into overall health status and organ function, which can be impacted by infection or inflammation.
  6. Lactate Dehydrogenase (LDH):

    • Purpose: To measure LDH levels, an enzyme that can be elevated in tissue damage or certain blood disorders.
    • Why Is It Ordered: To assess for tissue damage or specific types of hematologic conditions.

These tests, when ordered alongside a White Blood Cell Count test, provide a comprehensive evaluation of the immune system, infection, inflammation, and blood health. They are essential for diagnosing and managing a wide range of conditions, including infections, inflammatory diseases, and hematologic disorders. The specific combination of tests will depend on the individual's clinical presentation and the suspected underlying condition.

Conditions or Diseases Requiring a White Blood Cell Count Test

Several conditions or diseases can be associated with changes in the WBC:

  • Infections: Bacterial, viral, fungal, or parasitic infections can lead to elevated WBC counts.
  • Leukemia: A type of cancer that affects the blood and bone marrow, leading to abnormal white blood cell counts.
  • Bone Marrow Disorders: Conditions that affect the production of blood cells.
  • Immune System Disorders: Such as HIV, which can decrease WBC counts.
  • Inflammatory Diseases: Like rheumatoid arthritis or inflammatory bowel disease.
  • Severe Physical or Emotional Stress: Can cause a temporary increase in white blood cells.

Usage of White Blood Cell Count Test Results by Health Care Providers

An elevated WBC count (leukocytosis) may indicate an infection, inflammation, cancer, or other conditions. A low WBC count (leukopenia) could suggest a bone marrow problem, certain drugs, or diseases that suppress the immune system.

However, the WBC test is just one piece of the puzzle. The results must be interpreted in the context of a patient's clinical history, physical examination, and other laboratory results. Based on the findings, a healthcare provider will decide on the necessary treatments or interventions. For example, an infection might require antibiotics, while leukemia might lead to oncology consultations and specific treatments.

Most Common Questions About the White Blood Cell Count (WBC) test:

Understanding the Basics

What is the primary purpose of the White Blood Cell Count test?

The White Blood Cell Count (WBC) test measures the total number of white blood cells in a sample of a person's blood. White blood cells are a vital component of the immune system and play an essential role in fighting infections and responding to inflammation. The test is commonly used to detect or monitor infections, inflammatory diseases, and other conditions that can affect the number of white blood cells.

Medical Implications and Applications

Why might a physician order a White Blood Cell Count test?

A physician may order the White Blood Cell Count test as part of a routine health examination or if they suspect an infection, inflammation, certain types of cancer, or a bone marrow disorder. It can also be used to monitor the effects of medications or treatments, such as chemotherapy, that may impact the bone marrow's ability to produce white blood cells.

What diseases or conditions can cause a high or low white blood cell count?

A high white blood cell count, or leukocytosis, can be caused by various conditions, including infections, inflammation, stress, leukemia, tissue damage, or use of certain medications. A low white blood cell count, or leukopenia, may result from conditions like viral infections, bone marrow disorders, autoimmune diseases, or exposure to radiation or certain medications.

General Knowledge and Considerations

How does the White Blood Cell Count test differ from the Complete Blood Count test?

The White Blood Cell Count test specifically measures the number of white blood cells in a blood sample. In contrast, the Complete Blood Count (CBC) test provides a more comprehensive evaluation of the blood, measuring not only the white blood cells but also red blood cells, hemoglobin, hematocrit, and platelets. While the WBC test focuses solely on the immune system's cells, the CBC gives a broader view of overall health and potential issues related to the circulatory system.

Is there a need for any special equipment or technique to conduct the White Blood Cell Count test?

The White Blood Cell Count test is typically conducted using automated machines in a clinical laboratory. Blood is drawn from a vein, usually from the inside of the elbow, and the sample is then processed in the lab using hematology analyzers. These machines count the number of different types of cells in the blood quickly and accurately. Manual counts using a microscope can also be done if needed, but this is less common with modern technology.

Test Interpretation

If the results of the White Blood Cell Count test are abnormal, what are the next steps?

If the results of the White Blood Cell Count test are outside the normal range, it's essential to interpret them in the context of the patient's overall clinical picture, symptoms, and other laboratory findings. A single abnormal test result doesn't necessarily indicate a severe condition. The physician may order additional tests, like differential counts or blood cultures, to get a clearer understanding of the cause. Depending on the findings, treatment or further evaluation might be recommended.

Can other tests be combined with the White Blood Cell Count test for a more comprehensive diagnosis?

Yes, other tests can be combined with the White Blood Cell Count test to obtain a broader perspective of a patient's health. A differential white blood cell count can be done to determine the proportions of different types of white blood cells. Tests for red blood cells and platelets, such as the hemoglobin and hematocrit tests, can provide additional information about the blood's overall state and function. Combining multiple tests can aid in diagnosing conditions like anemia, clotting disorders, or specific types of leukemia.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.

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