A blood differential test can detect abnormal or immature cells. It can also diagnose an infection, inflammation, leukemia, or an immune system disorder.
Your doctor may order a blood differential test as part of a routine health exam.
A blood differential test is often part of a complete blood count (CBC). A CBC is used to measure the following components of your blood:
- white blood cells, which help stop infections
- red blood cells, which carry oxygen
- platelets, which help clot the blood
- hemoglobin, the protein in red blood cells that contains oxygen
- hematocrit, the ratio of red blood cells to plasma in your blood
A blood differential test is also necessary if your CBC results are not within the normal range.
Your doctor may also order a blood differential test if they suspect that you have an infection, inflammation, bone marrow disorder, or autoimmune disease.
A blood differential test examines the following types of white blood cells:
|Type of white blood cell
|helps stop microorganisms in infections by eating them and destroying them with enzymes
|–uses antibodies to stop bacteria or viruses from entering the body (B-cell lymphocyte)
–kills off the body’s cells if they’ve been compromised by a virus or cancer cells (T-cell lymphocyte)
|becomes a macrophage in the body’s tissues, eating microorganisms and getting rid of dead cells while increasing immune system strength
|helps control inflammation, especially active during parasite infections and allergic reactions, stops substances or other foreign materials from harming the body
|produces enzymes during asthma attacks and allergic reactions
Your doctor checks your white blood cell levels by testing a sample of your blood. This test is often performed at an outpatient clinical laboratory.
The healthcare provider at the lab uses a small needle to draw blood from your arm or hand. No special preparation before the test is necessary.
A laboratory specialist puts a drop of blood from your sample on a clear glass slide and smears it to spread the blood around. Then, they stain the blood smear with a dye that helps to differentiate the types of white blood cells in the sample.
The lab specialist then counts the number of each white blood cell type.
The specialist may do a manual blood count, visually identifying the number and size of cells on the slide. Your specialist might also use an automated blood count. In this case, a machine analyzes your blood cells based on automated measurement techniques.
Automated count technology uses electrical, laser, or photodetection methods to provide a highly accurate portrait of the size, shape, and number of blood cells in a sample.
A 2013 study showed that these methods are very accurate, even across different types of machines that do automatic blood counts.
Eosinophil, basophil, and lymphocyte count levels might not be accurate if you’re taking corticosteroid medications, such as prednisone, cortisone, and hydrocortisone, at the time of the test. Let your doctor know if you’re taking any of these medications before taking the test.
The risk of complications from having blood drawn is very slight. Some people experience mild pain or dizziness.
After the test, a bruise, slight bleeding, an infection, or a hematoma (a blood-filled bump under your skin) might develop at the puncture site.
Intense exercise and high levels of stress can affect your white blood cell count, especially your neutrophil levels.
Some studies show that a vegan diet can cause your white blood cell count to be lower than normal. However, the reason for this isn’t agreed upon by scientists.
An abnormal increase in one kind of white blood cell can cause a decrease in another kind. Both abnormal results can be due to the same underlying condition.
Lab values may vary. According to the American Academy of Pediatric Dentistry, the percentages of white blood cells in healthy people are as follows:
- 54 to 62 percent neutrophils
- 25 to 30 percent lymphocytes
- 0 to 9 percent monocytes
- 1 to 3 percent eosinophils
- 1 percent basophils
An increased percentage of neutrophils in your blood can mean that you have:
- neutrophilia, a white blood cell disorder that can be caused by an infection, steroids, smoking, or rigorous exercise
- an acute infection, especially a bacterial infection
- acute stress
- inflammation, such as inflammatory bowel disease or rheumatoid arthritis
- tissue injury due to trauma
- chronic leukemia
A decreased percentage of neutrophils in your blood can indicate:
- neutropenia, a white blood cell disorder that can be caused by a lack of neutrophil production in the bone marrow
- aplastic anemia, a decrease in the number of blood cells produced by your bone marrow
- a severe or widespread bacterial or viral infection
- recent chemotherapy or radiation therapy treatments
An increased percentage of lymphocytes in your blood may be due to:
- lymphoma, a white blood cell cancer that starts in your lymph nodes
- a chronic bacterial infection
- multiple myeloma, a cancer of the cells in your bone marrow
- a viral infection, such as mononucleosis, mumps, or measles
- lymphocytic leukemia
A decreased percentage of lymphocytes in your blood can be a result of:
- bone marrow damage due to chemotherapy or radiation treatments
- HIV, tuberculosis, or hepatitis infection
- a severe infection, such as sepsis
- an autoimmune disorder, such as lupus or rheumatoid arthritis
A heightened percentage of monocytes in your blood can be caused by:
- chronic inflammatory disease, such as inflammatory bowel disease
- a parasitic or viral infection
- a bacterial infection in your heart
- a collagen vascular disease, such as lupus, vasculitis, or rheumatoid arthritis
- certain types of leukemia
An increased percentage of eosinophils in your blood can indicate:
- eosinophilia, which can be caused by allergic disorders, parasites, tumors, or gastrointestinal (GI) disorders
- an allergic reaction
- skin inflammation, such as eczema or dermatitis
- a parasitic infection
- an inflammatory disorder, such as inflammatory bowel disease or celiac disease
- certain cancers
An increased percentage of basophils in your blood might be caused by:
- a serious food allergy
Your doctor will likely order more tests if you have a persistent increase or decrease in the levels of any of the listed types of white blood cells.
These tests can include a bone marrow biopsy to determine the underlying cause.
Your doctor will discuss management options with you after identifying the cause of your abnormal results.
They may also order one or more of the following tests to determine the best options for your treatment and follow-up:
- eosinophil count test
- flow cytometry, which can tell if a high white blood cell count is caused by cancers of the blood
- immunophenotyping, which can help find the best treatment for a condition caused by abnormal blood cell counts
- polymerase chain reaction (PCR) test, which measures biomarkers in bone marrow or blood cells, especially blood cancer cells
Other tests might be necessary based on the results of the differential test and follow-up tests.
Your doctor has many ways of determining and treating causes of abnormal blood cell counts, and your quality of life will likely remain the same, if not improve, once you find the cause.