Neutrophils are the most abundant type of white blood cell (typically 40-70% of circulating leukocytes) and function as the immune system’s first responders, migrating rapidly to sites of infection or injury to phagocytose bacteria and fungi. They are classified as granulocytes because their cytoplasm contains granules that stain neutral (neither strongly acidic nor basic) with Wright-Giemsa stain, distinguishing them from eosinophils (acidophilic) and basophils (basophilic). neutrophils mature in the bone marrow, progressing from myeloblast to band (immature, non-segmented nucleus) to segmented neutrophil (mature, multi-lobed nucleus); an increased proportion of bands relative to segs is termed a “left shift,” suggesting acute bacterial infection or marrow stress. Elevated neutrophil counts (neutrophilia) occur physiologically with stress, exercise, or corticosteroid use, and pathologically with bacterial infection, inflammation, or myeloproliferative disease; decreased counts ([[neutropenia]]) may be congenital, drug-induced (especially chemotherapy), infectious, or autoimmune, and predispose patients to serious, sometimes life-threatening infection. Neutrophil status is most commonly quantified clinically as the Absolute Neutrophil Count (ANC), a calculated value central to oncology and infectious disease management rather than a directly reported lab code.
The term was coined in the late 19th century by German pathologist Paul Ehrlich, a pioneer of hematologic staining techniques, who classified white blood cells by which dyes their granules absorbed: acidic (eosin) stains identified eosinophils, basic stains identified basophils, and cells whose granules took up neither strongly were termed “neutrophils” — literally “neutral-loving.” This staining-based naming convention links neutrophils to the broader granulocyte family alongside eosinophils and basophils.
Therapeutic, prophylactic, or diagnostic injection; subcutaneous or intramuscular (used for G-CSF administration)
HCPCS (supply/drug, not wikilinked per convention): J1442 (filgrastim), J1447 (tbo-filgrastim), Q5101 (filgrastim biosimilar) — used when billing G-CSF support for chemo-induced neutropenia.
⚠️ Coding Note:Category D70 requires etiology specificity — “low WBC” or “leukopenia” alone documented in the chart is not sufficient to assign a D70 code; query the provider to confirm the process is neutrophil-specific before coding. D70.1 (chemo-induced) and D70.2 (other drug-induced) require a companion adverse-effect T-code identifying the causative drug, with correct 7th character (A/D/S) matching encounter type — this pairing is frequently missed on inpatient profee claims and should trigger a query if only the neutropenia is documented. Sequencing: if neutropenia is the reason for the encounter (e.g., admission for febrile neutropenia monitoring), sequence the D70.- code first-listed with the T-code as an additional diagnosis per adverse effect guidelines; if the encounter is primarily for treatment of the underlying malignancy, sequence the neoplasm code first. D70.1/D70.2 frequently carry CC-level severity weight when documented as the reason for prolonged inpatient stay or isolation precautions — don’t let this specificity get buried under a nonspecific “pancytopenia” or “bone marrow suppression” note.