Neutrophils are one of five types of white blood cell (WBC) and make up between 40 - 60% of all WBC’s. They are also a type of granulocyte, cells which ingest foreign cells such as bacteria, viruses and parasites. Neutrophils are the primary cells that help fight infections and heal injuries and each neutrophil cell can ingest between 5 and 20 bacteria.
Neutrophils are measured as part of a full blood count. They can also be measured when people have frequent or unusual infections or when taking medication known to affect neutrophil levels.
High levels of neutrophils is called neutrophilia. In most cases, the increased number of neutrophils is a necessary reaction by the body to heal or fight an infection caused by bacteria, viruses, fungi or parasites. Neutrophils can however, be raised due inflammatory disease and autoimmune disorders like rheumatoid arthritis. Steroid medication can also cause raised neutrophils. Leukaemia may cause elevated levels of neutrophils and the number of neutrophils may also rise in people who have an injury, such as a fracture or burn.
Low levels of neutrophils is called neutropenia. The most common cause of neutropenia is infection and it is not associated with clinical problems but may contribute to mild neutropenia for several months after the illness. Another common cause of neutropenia is due to medications including painkillers/anti-inflammatories such as aspirin and ibuprofen, antibiotics, antidepressants, anticonvulsants and antihistamines. Neutropenia is also often a side effect of the treatment of cancer with chemotherapy or radiation therapy. A condition called benign ethnic neutropenia is relatively common in individuals of African, Middle Eastern or Jewish descent causing neutrophilia, but importantly, no increased risk of infection.
*It is important to note that blood neutrophil counts are not as stable as other blood cell counts and levels may vary over due to exercise, eating or the time of day. They can also vary during infections, in inflammatory disorders, during corticosteroid therapy or extreme anxiety. It is therefore important to consider the conditions and clinical backgrounds when the blood sample was obtained.