Ulta Lab Tests

White Blood Cell Count (WBC) and Differential

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The following is a list of what is included in the item above. Click the test(s) below to view what biomarkers are measured along with an explanation of what the biomarker is measuring.

Also known as: WBC, White Blood Cell Count WBC and Differential

Absolute Band Neutrophils (Only Reported If Detected)

Immature forms of neutrophils are called neutrophilic band cells. Neutrophils are a type of white blood cell that is responsible for much of the body's protection against infection. Neutrophils are produced in the bone marrow and released into the bloodstream to travel to wherever they are needed. Large numbers of immature forms of neutrophils, called neutrophilic band cells, are produced by the bone marrow when the demand is high.

Absolute Basophils

Basophils normally constitute 1% or less of the total white blood cell count but may increase or decrease in certain diseases and are thought to be involved in allergic reactions.

Absolute Blasts (Only Reported If Detected)

Blasts are immature forms of white blood cells.

Absolute Eosinophils

Eosinophils (eos) respond to infections caused by parasites and play a role in allergic reactions (hypersensitivities)

Absolute Lymphocytes

Lymphocytes are white blood cells that exist in both the blood and the lymphatic system. They are divided into three types. The B lymphocytes (B cells) are antibody-producing cells that are essential for acquired, antigen-specific immune responses. The second type are T lymphocytes (T cells) some T cells help the body distinguish between "self" and "non-self" antigens while others initiate and control the extent of an immune response, boosting it as needed and then slowing it as the condition resolves. Other types of T cells directly attack and neutralize virus-infected or cancerous cells. The third type are natural killer cells (NK cells) that directly attack and kill abnormal cells such as cancer cells or those infected with a virus.

Absolute Metamyelocytes (Only Reported If Detected)

Metamyelocytes are immature forms of white blood cells.

Absolute Monocytes

Monocytes (mono), similar to neutrophils, move to an area of infection and engulf and destroy bacteria. They are associated more often with chronic rather than acute infections. They are also involved in tissue repair and other functions involving the immune system.

Absolute Myelocytes (Only Reported If Detected)

Myelocytes are immature forms of white blood cells.

Absolute Neutrophils

Neutrophils (neu) normally make up the largest number of circulating WBCs. They move into an area of damaged or infected tissue, where they engulf and destroy bacteria or sometimes fungi. Young neutrophils, recently released into circulation, are called bands.

Absolute Nucleated Rbc (Only Reported If Detected)

Nucleated Red Blood Cells (nRBC) ) the presence of NRBCs in the adult blood is usually associated with malignant neoplasms, bone marrow diseases, and other serious disorders.

Absolute Promyelocytes (Only Reported If Detected)

Promyelocytes are immature forms of white blood cells.

Band Neutrophils (Only Reported If Detected)

Immature forms of neutrophils are called neutrophilic band cells. Neutrophils are a type of white blood cell that is responsible for much of the body's protection against infection. Neutrophils are produced in the bone marrow and released into the bloodstream to travel to wherever they are needed. Large numbers of immature forms of neutrophils, called neutrophilic band cells, are produced by the bone marrow when the demand is high.

Basophils

Basophils normally constitute 1% or less of the total white blood cell count but may increase or decrease in certain diseases and are thought to be involved in allergic reactions.

Blasts (Only Reported If Detected)

Blasts are immature forms of white blood cells.

Eosinophils

Eosinophils are specialized white blood cells produced in the bone marrow and released into the bloodstream, where they normally make up only 0–6 % of circulating leukocytes. Their cytoplasm is packed with reddish‑orange granules that contain potent enzymes (e.g., major basic protein, eosinophil cationic protein) and inflammatory mediators. When the immune system detects large, multicellular invaders—such as helminth (worm) parasites—eosinophils migrate out of the blood and surround the pathogen, releasing these granule contents to damage the parasite’s outer surface and aid its destruction. Beyond parasite defense, eosinophils act as key orchestras of the allergic response. They accumulate in tissues exposed to allergens (airways in asthma, skin in eczema, GI tract in eosinophilic esophagitis) and secrete cytokines and lipid mediators that amplify inflammation, recruit additional immune cells, and contribute to symptoms like swelling, mucus production, and itching. Because of this pro‑inflammatory role, persistently elevated eosinophil counts—termed eosinophilia—can signal allergic disorders, drug hypersensitivity, or certain autoimmune and malignant conditions. Conversely, counts drop toward zero after glucocorticoid therapy or in acute stress states, reflecting the cells’ sensitivity to hormonal and immune regulation.

Lymphocytes

Lymphocytes are white blood cells that exist in both the blood and the lymphatic system. They are divided into three types. The B lymphocytes (B cells) are antibody-producing cells that are essential for acquired, antigen-specific immune responses. The second type are T lymphocytes (T cells) some T cells help the body distinguish between "self" and "non-self" antigens while others initiate and control the extent of an immune response, boosting it as needed and then slowing it as the condition resolves. Other types of T cells directly attack and neutralize virus-infected or cancerous cells. The third type are natural killer cells (NK cells) that directly attack and kill abnormal cells such as cancer cells or those infected with a virus.

Metamyelocytes (Only Reported If Detected)

Metamyelocytes are immature forms of white blood cells.

Monocytes

Monocytes (mono), similar to neutrophils, move to an area of infection and engulf and destroy bacteria. They are associated more often with chronic rather than acute infections. They are also involved in tissue repair and other functions involving the immune system.

Myelocytes (Only Reported If Detected)

Myelocytes are immature forms of white blood cells.

Neutrophils

Neutrophils are a type of white blood cell that is responsible for much of the body's protection against infection. Neutrophils are produced in the bone marrow and released into the bloodstream to travel to wherever they are needed.

Nucleated Rbc (Only Reported If Detected)

Nucleated Red Blood Cells (nRBC) ) the presence of NRBCs in the adult blood is usually associated with malignant neoplasms, bone marrow diseases, and other serious disorders.

Promyelocytes (Only Reported If Detected)

Promyelocytes are immature forms of white blood cells.

Reactive Lymphocytes (Only Reported If Detected)

Lymphocytes are white blood cells that exist in both the blood and the lymphatic system. They are divided into three types. The B lymphocytes (B cells) are antibody-producing cells that are essential for acquired, antigen-specific immune responses. The second type are T lymphocytes (T cells) some T cells help the body distinguish between "self" and "non-self" antigens while others initiate and control the extent of an immune response, boosting it as needed and then slowing it as the condition resolves. Other types of T cells directly attack and neutralize virus-infected or cancerous cells. The third type are natural killer cells (NK cells) that directly attack and kill abnormal cells such as cancer cells or those infected with a virus.

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) and Differential test contains 1 test with 24 biomarkers .

Brief Description: The White Blood Cell Count and Differential test is a comprehensive analysis of the cellular components of the blood, specifically focusing on white blood cells (WBCs). This test provides insights into the different types of white blood cells present in the bloodstream and their respective percentages.

Also Known As: White Blood Cell Count Test, WBC Test, Leukocyte Test, Leukocyte Differential Test, White Count Test, Blood Differential Test, Diff Test, Peripheral Differential Test

Collection Method: Blood Draw

Specimen Type: Whole Blood

Test Preparation: No preparation required

When is a White Blood Cell Count and Differential test ordered?

A complete blood count, which may be carried out when a person gets a standard health assessment, is typically requested together with a WBC count. A person may undergo the test if they exhibit any of the following general indications of an infection or inflammation:

  • fever and chills
  • body discomfort and pains
  • headache
  • a number of additional symptoms, varying according to the likely site of infection or inflammation

When there are signs and symptoms that a doctor believes could be caused by a blood condition, an autoimmune disorder, or an immunological deficiency, testing may be done.

A WBC may be requested frequently and routinely to keep track of a patient who has been identified as having an infection, a blood or immunological problem, or another illness that affects WBCs. Additionally, it may be required when a particular therapy, like radiation or chemotherapy, is known to have an impact on WBCs in order to assess the efficacy of the treatment.

A complete blood count, which may be requested in conjunction with a standard physical examination, frequently includes the differential as part of the procedure.

If a differential is not performed concurrently with a CBC, it may be requested if the CBC findings go outside of the reference ranges.

What does a White Blood Cell Count and Differential test check for?

Leukocytes, commonly known as white blood cells, are circulating lymphatic and blood cells that aid in the body's defense against infection. They have a key function in the body's immune system, as well as in inflammation, allergic reactions, and cancer prevention. The total number of each type of WBC in a person's blood sample is known as the WBC difference.

White blood cells come in five different varieties, each of which has a unique purpose. The differential shows if the cells are distributed normally in relation to one another, whether one cell type is more or less prevalent, and/or whether aberrant and/or immature cells are present. The diagnosis of particular disorders that impact the immune system and bone marrow can be helped by the information provided.

A complete blood count, which is frequently used as a routine health checkup, may be combined with a differential, or it may be used as a follow-up to aberrant CBC results. The most common way to perform a differential is using an automated blood analyzer, but it can also be done manually by a skilled laboratory technician looking at a blood smear under a microscope. The data can be given as relative percentages of the total number of WBCs but are commonly expressed as absolute numbers of cells.

Precursor cells made in the bone marrow give rise to white blood cells. The five different kinds of WBCs are as follows:

These white blood cells, called granulocytes, have granules in their cytoplasm. The chemicals and other materials in the granules are released as a result of an immunological response. There are three different kinds of granulocytes:

Normally, the majority of WBCs in circulation are neutrophils. They enter a damaged or contaminated tissue area where they consume and kill bacteria and occasionally fungus.

Eosinophils react to parasite infections, contribute to allergy reactions, and regulate the intensity of immunological reactions and inflammation.

It is believed that basophils, which typically make up the smallest percentage of circulating WBCs, are implicated in allergic reactions.

Blood and the lymphatic system both include lymphocytes. Although they are split up into three sorts, the differential does not make a distinction between them. From shared lymphoid progenitor cells in the bone marrow, all lymphocytes develop. All lymphocytes are counted and reported together by the differential. The three categories must be distinguished using various, specialist testing:

The production of antibodies by B lymphocytes is necessary for adaptive, antigen-specific immune reactions. B-cells that have completed their differentiation into plasma cells create antibodies, which are immunological proteins that hunt down and eliminate bacteria, viruses, and other "non-self" foreign antigens.

T cells are made up of a few different types and complete their maturation in the thymus. The body can discriminate between "self" and "non-self" antigens with the aid of some T cells. Others start and regulate the size of an immune response, raising it as necessary and then reducing it as the illness gets better. Other T cell subtypes target and kill malignant or virus-infected cells directly.

Natural killer cells go after and kill aberrant cells like cancerous or virus-infected ones directly.

Similar to neutrophils, monocytes migrate to an infection site, engulfing and killing germs. They are more frequently linked to chronic infections than acute ones. They also play a role in immune system-related processes like tissue healing.

The bone marrow makes more WBCs and releases them into the blood when there is an infection or an inflammatory event anywhere in the body. One type of WBC may be elevated above others depending on the origin of the infection or inflammation. The creation of that kind of WBC declines as the disease gets better, and the number returns to normal.

The creation of WBCs by the bone marrow or their survival in the blood can be impacted by a number of illnesses, in addition to infections and inflammation, and this can lead to either increased or decreased numbers. The differential notifies the healthcare provider of any potential health problems, together with the other CBC components. The existence of aberrant and/or immature populations of WBCs can be detected by additional tests, such as a blood smear review, which is frequently used to interpret the results.

Some immature cell types are discharged from the bone marrow into the circulation in a few critical disorders, and the WBC differential may be used to identify them. This could happen as a result of a bacterial infection, leukemia, a solid tumor affecting the bone marrow, the myelodysplastic syndrome, or myeloproliferative neoplasms, for instance. Myelocytes, promyelocytes, blasts, and metamyelocytes are a few immature cells that could be found.

A wide range of additional tests may be carried out to help identify the issue's root cause if results point to a problem. When determining what additional tests could be required, a healthcare professional will frequently take into account a patient's indications and symptoms, medical history, and the outcomes of a physical examination. For instance, a bone marrow biopsy will be carried out as needed to assess the bone marrow status.

Lab tests often ordered with a White Blood Cell Count and Differential test:

When a WBC Count and Differential test is ordered, it's often part of a broader evaluation of the body's health and immune function. Here are some tests commonly ordered alongside it:

  1. Complete Blood Count (CBC):

    • Purpose: To evaluate overall blood health, including red blood cells, white blood cells, hemoglobin, hematocrit, and platelets.
    • Why Is It Ordered: To assess the general health status and to diagnose a variety of conditions, such as anemia, infection, and blood disorders.

  2. Blood Culture:

    • Purpose: To detect the presence of bacteria or fungi in the bloodstream.
    • Why Is It Ordered: To identify the cause of an infection, especially in cases of suspected sepsis or systemic infection.

  3. C-Reactive Protein (CRP) or Erythrocyte Sedimentation Rate (ESR):

    • Purpose: To measure markers of inflammation in the body.
    • Why Is It Ordered: To assess for inflammation and help determine the severity and cause of certain conditions like infections and autoimmune diseases.

  4. Procalcitonin:

    • Purpose: To measure the level of procalcitonin, a marker that can increase in bacterial infections.
    • Why Is It Ordered: To help distinguish bacterial infections from other causes of inflammation or infection, particularly in critical care settings.

  5. Liver Function Test:

    • Purpose: To assess liver health.
    • Why Is It Ordered: To evaluate liver function, as liver disorders can impact blood cell production and overall health.

  6. Kidney Function Test:

    • Purpose: To assess kidney function.
    • Why Is It Ordered: To evaluate kidney health, as kidney disorders can affect the balance of electrolytes and fluids, which in turn can influence blood cell counts.

These tests, when ordered alongside a WBC Count and Differential, provide a comprehensive evaluation of the body's health, particularly the immune system and blood-related disorders. They are crucial for diagnosing and managing infections, inflammation, hematological conditions, and immune system disorders. The specific combination of tests will depend on the individual’s symptoms, clinical presentation, and medical history.

Conditions where a White Blood Cell Count and Differential test is recommended:

The White Blood Cell Count and Differential test is essential in diagnosing and monitoring a variety of conditions, including:

  1. Infections: Abnormal levels of specific white blood cells can indicate bacterial, viral, fungal, or parasitic infections.

  2. Immune Disorders: Conditions like leukemia, autoimmune disorders, and allergies can affect white blood cell counts and proportions.

  3. Inflammatory Conditions: Chronic inflammatory conditions like rheumatoid arthritis and inflammatory bowel disease can impact white blood cell distributions.

How does my health care provider use a White Blood Cell Count and Differential test?

The white blood cell count is used to:

Check for a variety of illnesses and disorders

  • Determine the existence of various diseases that influence WBCs, such as allergies, leukemia, or immunological disorders, to mention a few; assist in the diagnosis of an infection or inflammatory process.
  • WBC counts may be used to track the evolution of illnesses like those mentioned above, the body's reaction to different therapies, and/or the health of the bone marrow. Some treatments, like radiation and chemotherapy, are known to alter white blood cells and may be tracked using WBC counts.

White blood cells are a vital component of the body's immune system and can be found in the blood, lymphatic system, and tissues. Some illnesses make the immune system react, which results in an increase in WBCs. The amount of circulating WBCs can change depending on other factors that impact the bone marrow's ability to produce WBCs or the survival of WBCs in the circulation.

The presence of a disease or condition that affects white blood cells can be detected by a WBC count, but the underlying cause cannot be established. To assist in making a diagnosis, a number of additional tests could be carried out concurrently or as a follow-up to an aberrant result. A WBC differential, a blood smear review, or in extreme cases, a bone marrow examination may be a few of these extra tests. While a blood smear and/or bone marrow biopsy can show the existence of aberrant and/or immature WBCs, a differential can identify which type of WBC is low or high.

A complete blood count is frequently used as part of a general health check to determine the white blood cell differential. When a CBC shows a high or low white blood cell count, it may be utilized to assist identify the cause. Other illnesses and ailments that impact one or more different types of WBCs may also be monitored and/or helped with the diagnosis.

Neutrophils, lymphocytes, monocytes, eosinophils, and basophils are the five different types.

The differential counts all the cells of each kind and assesses whether they are distributed in their expected ratios, whether one cell type is increased or decreased, or whether any immature cells are present. These details are helpful in determining the precise origin of an illness, including:

  • bacterial, viral, fungal, or parasitic infections
  • Inflammation
  • asthma and allergies
  • autoimmune diseases
  • Leukemia
  • The Myelodysplastic Syndrome
  • A myeloproliferative tumor

Specific types of WBCs rise as a result of the immune system's reaction to some diseases. A difference may provide information about the precise origin of that immune response. For instance, it might be used to identify if a virus or bacterium is to blame for an infection.

Other factors impact the amount of specific WBCs by reducing or increasing their production by the bone marrow or by reducing their survival in the blood. The healthcare provider can determine which type of WBC is low or high using a differential.

Other tests, such as a blood smear, bone marrow biopsy, chromosomal analysis, or immunophenotyping, may be performed after an aberrant differential result. These examinations may detect populations of WBCs that are aberrant or immature.

What do my White Blood Cell Count and Differential test results mean?

A WBC count shows if there has been a general rise or fall in the quantity of white blood cells. A health professional will take into account a variety of additional aspects, including a physical examination, medical history, and signs and symptoms, in addition to the results of a WBC count and other parts of a complete blood count.

Numerous illnesses and circumstances can cause leukocytosis, a high white blood cell count. Several instances include:

  • Bacteria, some viruses, and less frequently fungi or parasites, are the most prevalent causes of infections.
  • inflammation or inflammatory diseases such inflammatory bowel illness, vasculitis, or rheumatoid arthritis
  • Myeloproliferative neoplasms and leukemia
  • conditions that cause tissue death, such as heart attack, surgery, burns, or trauma
  • Allergy symptoms

Leukopenia, a low white blood cell count, can be brought on by illnesses like:

  • loss of bone marrow
  • Disorders of the bone marrow in which it fails to manufacture enough WBCs
  • malignancy that has spread to the bone marrow, such as lymphoma
  • Autoimmune diseases: the body targets and kills its own white blood cells
  • nutritional deficits
  • excessive infections
  • immune system disorders that kill T cells, like HIV

When WBC counts are used as a monitoring tool, a string of WBC counts that rise or fall to abnormally high or low levels signifies that the condition or disease is deteriorating. WBC counts returning to normal signify progress and/or a successful course of treatment.

The results of a differential show how many and/or what proportion of each type of white blood cell are present in the sample of blood taken from the subject.

Results of a differential are often presented as the absolute values of the five different types of WBCs and/or as a percentage of all WBCs. Calculating absolute values involves multiplying the total number of white blood cells by the proportion of each type of white cell. This data can help with both disease diagnosis and treatment monitoring. The majority of WBC are normally neutrophils, followed by lymphocytes, monocytes, eosinophils, and basophils.

When analyzing the outcomes of a differential, caution must be used. A healthcare professional will take into account a patient's indications and symptoms, medical history, and the degree of cell growth or decline. Any one type of cell's population can briefly increase or decrease due to a variety of circumstances. Further testing to identify the cause is typically prompted by an ongoing increase or reduction.

In some circumstances, blood may contain immature and/or aberrant types of the cells, which can be found using a differential. Metamyelocytes, myelocytes, promyelocytes, and/or blasts are examples of immature forms. There may be a need for more testing.

Most Common Questions About the White Blood Cell Count and Differential test:

Purpose and Clinical Significance

What is the White Blood Cell Count and Differential test?

The White Blood Cell Count and Differential test is a commonly ordered blood test that measures the total number of white blood cells (WBCs) in a blood sample and provides a count of the different types of white blood cells, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils.

Why is the White Blood Cell Count and Differential test important?

The test provides insights into a patient's immune system and helps diagnose conditions like infections, inflammation, allergies, leukemia, and other disorders that can affect white blood cells. It also assists in monitoring the effectiveness of treatments for these conditions.

Interpretation of Results

What does a high white blood cell count indicate in the White Blood Cell Count and Differential test?

An elevated WBC count, or leukocytosis, often suggests an infection, inflammation, tissue damage, or certain cancers like leukemia. The specific type of white blood cell that's increased can provide further insights. For instance, a rise in neutrophils might indicate a bacterial infection, while increased eosinophils might suggest an allergic reaction.

How are results from the White Blood Cell Count and Differential test used in conjunction with other tests?

The results are often used alongside other tests, such as a complete blood count (CBC), to give a comprehensive overview of a patient's health. For instance, if a patient has a low red blood cell count (anemia) and a high WBC count, it might indicate a bone marrow disorder.

Disease and Complications

How does the White Blood Cell Count and Differential test help in diagnosing leukemia?

In leukemia, the bone marrow produces abnormal white blood cells. These cells can be identified by their appearance and quantity in the blood. A significant increase in WBCs, especially immature forms, can be suggestive of leukemia.

Does a low white blood cell count in the White Blood Cell Count and Differential test always signify a health issue?

A low WBC count, known as leukopenia, can be due to various reasons, including viral infections, bone marrow disorders, autoimmune conditions, certain medications, and more. While a low count does raise concerns, the cause might also be benign or transient. The specific type of white blood cell that's decreased and other clinical findings provide a clearer picture.

Relation with Other Tests

How does the White Blood Cell Count and Differential test compare to a basic CBC?

While a complete blood count (CBC) provides an overall count of white blood cells, red blood cells, and platelets, the differential test goes a step further by breaking down the WBC count into its different cell types, giving more detailed information about the immune system's status.

Why might a doctor order both a White Blood Cell Count and Differential test and a platelet count?

Both tests offer insights into the bone marrow's functioning. While the WBC count focuses on the immune response, the platelet count provides information on clotting. A simultaneous decrease in both might suggest a bone marrow issue or a systemic condition affecting blood cell production.

Understanding the results of the White Blood Cell Count and Differential test in the context of a patient's overall health, symptoms, and other test outcomes is crucial for accurate diagnosis and effective treatment planning.

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

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