countneutrophils

Countneutrophils, or neutrophil count, refers to the number of neutrophils in peripheral blood. Neutrophils are the most abundant white blood cells and form a first line of defense in the innate immune system, helping to contain and eliminate bacterial and fungal infections.

In clinical practice the neutrophil count is usually reported as an absolute neutrophil count (ANC) or as a percentage of white blood cells on a complete blood count with differential. The ANC is calculated as ANC = WBC × (percentage of segmented neutrophils + percentage of band neutrophils). Units are typically x10^9/L or cells per microliter. Normal ranges vary by age and laboratory; in healthy adults the ANC is roughly 1.5 to 8.0 x10^9/L, with pediatric and neonatal values differing somewhat.

Abnormal values have specific clinical implications. Neutropenia is an ANC below the normal range, commonly classified as mild (about 1.0–1.5 x10^9/L), moderate (0.5–1.0 x10^9/L), or severe (<0.5 x10^9/L). Neutrophilia is an elevated count, often defined as an ANC above about 7.5 x10^9/L, and can occur with acute bacterial infections, inflammation, stress, medications such as corticosteroids, smoking, or after strenuous exercise.

The ANC is used to assess infection risk, monitor patients undergoing chemotherapy, and guide clinical decisions. A low ANC increases susceptibility to infections and may prompt protective measures or therapeutic interventions. It is important to recognize that the count does not measure neutrophil function, and other clinical factors may influence interpretation. Additionally, counts can be affected by diurnal variation and laboratory methods.