Neutrophils
Overview
Neutrophils measure the absolute number or percentage of circulating neutrophils, the most abundant white blood cell type that serves as the first line of defense against bacterial and fungal infections through phagocytosis and release of antimicrobial granules. These granulocytes migrate rapidly to infection sites, forming pus and contributing to acute inflammatory responses. Elevated levels (neutrophilia) indicate bacterial infections, inflammation, stress, or myeloproliferative disorders, while low levels (neutropenia) suggest viral infections, bone marrow suppression, or autoimmune destruction. Clinically, neutrophil counts guide infection management, chemotherapy dosing, and sepsis risk assessment.
Clinical Use Cases
- Diagnosing and monitoring bacterial infections and sepsis.
- Assessing chemotherapy-induced neutropenia and infection risk.
- Evaluating inflammatory conditions (rheumatoid arthritis, gout).
- Monitoring chronic myeloid leukemia and other myeloproliferative disorders.
Specimen Types
- Whole blood (EDTA anticoagulant).
Measurement Methods
- Automated hematology analyzer (flow cytometry, impedance).
- Manual differential count on Wright-Giemsa stained smear.
- Fluorescence flow cytometry for advanced analyzers.
Test Preparation and Influencing Factors
- No fasting required; diurnal variation with morning peak.
- Corticosteroids, epinephrine, and acute stress cause demargination neutrophilia.
- Recent viral infections transiently lower counts.
- Pregnancy causes physiologic neutrophilia in third trimester.
Synonyms
- Absolute neutrophil count (ANC).
- Polymorphonuclear leukocytes (PMNs).
- Segmented neutrophils.