Seeing an abnormal outcome on your lab test may be alarming, especially when you don’t understand what the terms on your report mean. For example, it’s normal to be concerned if you see high or low levels of eosinophils on your blood tests.
City of Hope® sat down with Delu Zhou, M.D., Ph.D., a pathologist with City of Hope Cancer Center Chicago, to find out what eosinophils mean on lab testing. This article covers the basics on eosinophils, including:
- What are eosinophils?
- How are eosinophil counts measured?
- What do the levels mean on blood tests?
- What level of eosinophils indicates cancer?
- What do abnormal eosinophil levels mean for cancer patients?
- Next steps
If you or a loved one is concerned about possible signs or symptoms of cancer and would like an initial appointment or a second opinion, call us 24/7 at (877) 524-4673.
What Are Eosinophils?
“Eosinophils are a type of white blood cell,” Dr. Zhou says. White blood cells may also be referred to as leukocytes.
“Eosinophils function as immune cells and play an important role in fighting off parasitic infections and mediating the human body’s response in allergic disorders,” Dr. Zhou notes.
How Are Eosinophil Counts Measured?
Eosinophils are most commonly measured in peripheral blood, which is the blood that moves through your circulatory system. “This test is usually ordered as complete blood count (CBC) with differential,” Dr. Zhou says. “But this is not the only way to measure eosinophils, which can migrate from blood to tissue, especially during certain inflammatory conditions. Eosinophils can also be measured in tissue samples under microcopy to evaluate local inflammation.”
For example, a pathologist may evaluate the patient’s intraepithelial eosinophils (those found in the lining of an organ) as a way to diagnose eosinophilic esophagitis, a chronic condition that causes inflammation in the esophagus.
What Do Eosinophil Levels Mean on Blood Tests?
The eosinophil levels on your test results indicate how many eosinophils are present in the sample that was analyzed. If your care team performed a blood test, a normal eosinophil level would typically be less than 500 eosinophils per microliter of blood, Dr. Zhou says.
Eosinophils High
If you have 500 or more eosinophils per microliter of blood, your care team would consider that to be a high eosinophil count, Dr. Zhou explains.
An increased number of eosinophils in your blood is also called eosinophilia. This may have many causes, including:
- Allergic disorders
- Certain autoimmune diseases
- Parasitic infections
- Certain types of cancer, such as myeloid neoplasms and certain lymphomas
- Hypereosinophilic syndrome
A slightly elevated eosinophil level would require a closer look by your care team, but if the number is significantly higher than normal (over 5,000 eosinophils per microliter of blood is considered severe eosinophilia), your care team may investigate immediately. “Extremely high number of eosinophils may cause organ damage,” Dr. Zhou says.
Eosinophils Low
If your eosinophil count is below 30 eosinophils per microliter of blood, that’s considered low. “Low eosinophil counts have much less clinical significance,” Dr. Zhou says. “They may be associated with excess production of cortisol, steroid use or certain acute infections.”
What Level of Eosinophils Indicates Cancer?
“While eosinophilia can be associated with a variety of conditions, there is no definitive level to indicate that a patient has cancer,” Dr. Zhou says. “When eosinophilia has no known causes and is persistent, further investigation to rule out cancer is needed.”
Cancer can’t be definitively diagnosed based on eosinophil counts alone. If you have high eosinophil counts, your care team will combine clinical, pathomorphological and molecular information to diagnose or rule out cancer.
What Do Abnormal Eosinophil Levels Mean for Cancer Patients?
If someone has already been diagnosed with cancer, the care team may review eosinophil counts as part of routine periodic lab testing.
For certain blood cancers, checking eosinophils may help the care team evaluate the patient’s treatment response, Dr. Zhou says. “The test can also be used to monitor the side effects of cancer treatment. For example, cancer immunotherapy is known to cause an increased number of eosinophils in some patients. The test may also help to monitor the immune response and inflammatory or allergic-type reactions in cancer patients.”
Next Steps
If your lab test shows abnormal eosinophil levels, reach out to the care team to discuss what to do next. They’ll explain whether you should get further testing or an additional evaluation to figure out what may be going on.
If you or a loved one is concerned about potential signs or symptoms of cancer and would like an initial appointment or a second opinion, call us 24/7 at (877) 524-4673.