Understanding your labs: White Blood Cell Count
White blood cells are crucial components of our immune system, and measuring their levels in the blood can provide important information, especially for those undergoing cancer treatment. Since blood counts can be complex, we aim to simplify the key aspects of white blood cell counts for you. Our goal is to help you understand your labs and what your provider is referencing during your visit.
Complete blood count (CBC) - the measure of the cells in circulation in your blood. The CBC looks at white blood cells which are a part of the immune systems, red blood cells which carry oxygen throughout the body, and platelets which function to clot the blood when needed.
All blood cells are made in your bone marrow. When they are mature and ready to perform their functions, they are pushed out into circulation in your blood vessels. This is where we can measure the CBC and the individual cell lines.
White blood cell count (WBC) - the total number of white blood cells that are circulating in the blood. White blood cells are a part of the immune system. There are 5 types of white blood cells and each type has a different focus in the immune system.
Differential - reports the 5 different white blood cell lines. The differential includes an absolute number (total number measured of the that cell line) and a percentage (of that specific cell line in comparison to all of the white blood cell lines. Add all 5 cell line percentages together to make 100%)
Types of white blood cells:
neutrophils (also know as segs, segmented neutrophils, or granulocytes - don’t all of these interchangeable names drive you crazy!)
lymphocytes
monocytes
eosinophils
basophils
Neutrophils are important and of interest when someone is going through cancer treatment because they are the first line of defense to fight off infections.
Neutropenia is the medical term for low neutrophils
Immunocompromised the medical term for an individual that does not have a fully functioning immune system, as in the case of having low neutrophils or neutropenia. Immunocompromised means an individual is at increased risk for infections.
In cancer care, neutrophils are of particular importance since they are the first line of defense to fight off infection. Some treatments (especially specific chemotherapies) increase the risk of having a compromised immune system by decreasing the production of certain cells in the bone marrow, including neutrophils. It is important to know if a drug you are receiving may affect the neutrophil count as there are precautions you may need to take to prevent infection.
If you are on a drug that affects the neutrophil count, there has been extensive research into when the neutrophil count drops and when it will recover. When the neutrophil count hits the lowest point, this is know as the nadir. You may see this term with a range of days in some literature you received on your drug. During this range, an individual is at the highest risk for infection. This is an important time to practice good hand hygiene and stay away from others that may be ill. The nadir help determine cycling intervals of the treatment as chemotherapy is usually not administered until the neutrophil count returns to an adequate range. Once the nadir is reached, we know the bone marrow kicks in to produce more neutrophils and they will continue to rise and recover.
If you develop symptoms of an infection while your neutrophil count is low, it's crucial to inform your care team immediately. Infections during neutropenia may require antibiotics, and in some cases, hospitalization, and can be life-threatening.
Depending on the chemotherapy regimen, grow factors that stimulate the neutrophil count (Neupogen, Neulasta) may be used. These can help keep the neutrophil count high enough so interruptions in cycling of chemotherapy can be minimized. They are not used with all treatment regimens, only ones that are high risk for neutropenia.
Knowledge is power. Neutropenia is one of the many symptoms we discuss in our Field Guide to Chemotherapy Symptom Management. It is important to understand what precautions to take if you are neutropenic. Infectious symptoms can be masked and the infection can become serious quickly. If you or someone you know is undergoing chemotherapy, check out our Field Guides that are available for download.