Determining absolute neutrophil count (ANC) involves multiplying the total white blood cell count by the percentage of neutrophils (segmented neutrophils plus band neutrophils) in a differential blood count. For instance, if a patient’s white blood cell count is 8,000 cells/L and the differential shows 60% segmented neutrophils and 10% band neutrophils, the ANC is 8,000 x (0.60 + 0.10) = 5,600 cells/L.
This calculation provides critical information for assessing a patient’s risk of infection. A low ANC, termed neutropenia, signifies a weakened immune system, increasing susceptibility to bacterial and fungal infections. Monitoring and understanding this value is essential for guiding treatment decisions, such as prophylactic antibiotics or growth factors, and for implementing protective measures to minimize infection risk. Historically, the development of this calculation represented a significant advance in patient care, providing a quantifiable measure for assessing immune status.