Blood Differential Test

The blood differential test measures the percentage of each type of white blood cell (WBC) that you have in your blood. It also reveals if there are any abnormal or immature cells.

Five types of white blood cells, also called leukocytes, normally appear in the blood:

Neutrophils
Lymphocytes
Monocytes

Eosinophils
Basophils

A special machine or a health care provider counts the number of each type of cell. The test shows if the number of cells are in proper proportion with one another, and if there is more or less of one cell type.

Why the Test is Performed

This test is done to diagnose an infection, anemia, or leukemia. It may also be used to monitor one of these conditions, or to see if treatment is working.

Normal Results

The different types of white blood cells are given as a percentage:

Neutrophils: 40% to 60%
Lymphocytes: 20% to 40%

Monocytes: 2% to 8%
Eosinophils: 1% to 4%

Basophils: 0.5% to 1%

What Abnormal Results Mean

Any infection or acute stress increases your number of white blood cells. High white blood cell counts may be due to inflammation, an immune response, or blood diseases such as leukemia.

It is important to realize that an abnormal increase in one type of white blood cell can cause a decrease in the percentage of other types of white blood cells.

An increased percentage of neutrophils may be due to:

Acute infection
Acute stress
Eclampsia (seizures or coma in a pregnant woman)
Gout (type of arthritis due to uric acid buildup in the blood)

Acute or chronic forms of leukemia
Myeloproliferative diseases
Rheumatoid arthritis
Rheumatic fever (disease due to an infection with group A streptococcus bacteria)

Thyroiditis (a thyroid disease)
Trauma
Cigarette smoking

A decreased percentage of neutrophils may be due to:

Aplastic anemia
Chemotherapy

Influenza (flu)
Radiation therapy or exposure

Viral infection
Widespread severe bacterial infection

An increased percentage of lymphocytes may be due to:

Chronic bacterial infection
Infectious hepatitis (liver swelling and inflammation from bacteria or viruses)
Infectious mononucleosis, or mono (viral infection that causes fever, sore throat, and swollen lymph glands)

Lymphocytic leukemia (a type of blood cancer)
Multiple myeloma (a type of blood cancer)
Viral infection (such as mumps or measles)

A decreased percentage of lymphocytes may be due to:

Chemotherapy
HIV/AIDS infection
Leukemia
Radiation therapy or exposure

Sepsis (severe, inflammatory response to bacteria or other germs)
Steroid use

An increased percentage of monocytes may be due to:

Chronic inflammatory disease
Leukemia
Parasitic infection

Tuberculosis, or TB (bacterial infection that involves the lungs)
Viral infection (for example, infectious mononucleosis, mumps, measles)

An increased percentage of eosinophils may be due to:

Addison disease (adrenal glands do not produce enough hormones)
Allergic reaction
Cancer

Chronic myelogenous leukemia
Collagen vascular disease

Hypereosinophilic syndromes
Parasitic infection

An increased percentage of basophils may be due to:

After splenectomy
Allergic reaction
Chronic myelogenous leukemia (a type of bone marrow cancer)

Collagen vascular disease
Myeloproliferative diseases (group of bone marrow diseases)
Chickenpox

A decreased percentage of basophils may be due to:

Acute infection

Cancer

Severe injury

References

1. Chernecky CC, Berger BJ. Differential leukocyte count (diff) - peripheral blood. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders; 2013:440-446.

2. Hutchison RE, Schexneider KI. Leukocytic disorders. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 33.

3. Review Date: 1/29/2019

4. Updated by: Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

The medical information provided is for informational purposes only and is not to be used as a substitute for professional medical advice, diagnosis or treatment. Please contact your health care provider with questions you may have regarding medical conditions or the interpretation of test results.