Overview
Neutrophils (polymorphonuclear neutrophils, PMNs) are mature granulocytic leukocytes characterized by a segmented nucleus and fine neutral-staining cytoplasmic granules on Wright-Giemsa stain.
They are the predominant granulocyte in peripheral blood and the primary circulating phagocyte against extracellular bacteria.
Classification
| Category | Term |
|---|---|
| Lineage | Myeloid, granulocyte |
| Synonyms | PMN; neutrophilic granulocyte; seg (segmented form) |
| Maturation stage (peripheral) | Segmented (mature) → band (immature) |
| Related cells | Eosinophil, basophil (other granulocytes); monocyte (myeloid) |
| Marrow precursors | Myeloblast → promyelocyte → myelocyte → metamyelocyte → band → segmented |
Morphologic Features
Identify neutrophils on peripheral smear by nuclear shape, lobulation, and granule character. Reactive changes alter cytoplasmic appearance without necessarily changing total neutrophil count.
| Form / finding | Nucleus | Cytoplasm | Significance |
|---|---|---|---|
| Segmented neutrophil | 2–5 lobes connected by filaments | Fine pink/lavender granules | Mature circulating form |
| Band neutrophil | Horseshoe or C-shaped; unsegmented | Fine granules | Immature form; ↑ in left shift |
| Toxic granulation | Variable | Coarse, dark granules | Reactive, infection/inflammation |
| Döhle bodies | Variable | Pale blue cytoplasmic inclusions | Often reactive with toxic granulation; congenital/MYH9-related forms exist |
| Hypersegmentation | ≥6 lobes and/or >3% with 5 lobes | Normal granules | Megaloblastic deficiency common; also MDS, renal disease, drugs, hereditary forms |
| Cytoplasmic vacuolation | Variable | Clear vacuoles in cytoplasm | Reactive stress, toxic changes, or artifact |
Segmented neutrophil
Multilobed nucleus; fine cytoplasmic granules.
Band neutrophil
Horseshoe nucleus without filamentous constriction.
Toxic granulation
Coarse granules, reactive change; correlate clinically.
Laboratory Characteristics
- CBC with differential: WBC, neutrophil %, band % (if reported), immature granulocyte (IG) fraction on some analyzers
- Calculated ANC, institutional protocol may include band forms in the neutrophil fraction
- Automated flags: left shift, IG present, neutropenia, neutrophilia, blast/abnormal lympho
- Reflex smear review per institutional criteria when flags, critical ANC, or delta-check discordance
- Manual differential: 100-cell leukocyte count; classify band vs segmented; note toxic changes
- Related assays: peripheral smear, bone marrow examination (unexplained cytopenia), vitamin B12/folate (hypersegmentation)
Reference Intervals
Typical adult reference intervals, verify against the population served and institutional intervals (CLSI EP28-A3c). Pediatric age-stratified intervals differ and are not listed here.
| Parameter | Typical adult reference | Notes |
|---|---|---|
| WBC | 4.0–10.0 × 10⁹/L | Denominator for differential percentages |
| Neutrophil % | 40–70% | Interpret with calculated ANC |
| ANC | 1.5–8.0 × 10⁹/L (typical adult teaching range) | Institution- and population-specific; calculate from WBC × neutrophil fraction |
| Band forms | ≤6% at many institutions | Elevated in left shift; not equivalent to IG fraction |
| Critical ANC notification | Often ≤0.5 × 10⁹/L | Institution-specific critical value per CLSI GP47-Ed1, not interchangeable with severity grade alone |
Clinical and Laboratory Significance
| Finding | Laboratory pattern | Clinical significance |
|---|---|---|
| Neutrophilia | ↑ WBC and/or ↑ ANC | Infection, inflammation, tissue injury, demargination (e.g., glucocorticoids) |
| Left shift | ↑ band forms; IG flag or immature forms on smear | Accelerated granulopoiesis; confirm on smear |
| Toxic granulation | Smear finding ± neutrophilia | Reactive stress; does not alone confirm bacteremia |
| Neutropenia | ↓ ANC | Infection risk; grade by ANC severity |
| Hypersegmentation | Smear finding ± macrocytosis | Vitamin B12 or folate deficiency among other causes, correlate studies |
| Persistent neutrophilia | Serial ↑ ANC without toxic changes | Consider MPN; hematology correlation |
| Leukoerythroblastic response | nRBCs + immature myeloid forms on smear | Marrow stress or infiltration, distinct from uncomplicated left shift |
Differential Considerations
Branch by integrated CBC, differential, and smear pattern, not by isolated percentage elevation.
| Pattern | Key findings | Primary considerations |
|---|---|---|
| Reactive neutrophilia | ↑ ANC, left shift, toxic granulation | Bacterial infection, inflammation, tissue necrosis |
| Demargination | ↑ ANC, minimal smear changes | Glucocorticoids, epinephrine, stress |
| Megaloblastic | Macrocytosis, hypersegmented neutrophils, ↓ ANC possible | Vitamin B12 or folate deficiency |
| Myeloproliferative | Persistent leukocytosis, basophilia, left shift without toxic changes | CML, other MPN . WHO classification applies |
| Neutropenic | Critical or severe ↓ ANC | Drug effect, marrow failure, immune destruction, sequestration |
Comparison Tables
Segmented vs band neutrophil
| Feature | Segmented neutrophil | Band neutrophil |
|---|---|---|
| Nuclear shape | Multilobed (2–5 lobes) | Horseshoe; no thin filament between lobes |
| Maturity | Mature | Immature circulating form |
| Left shift | Predominant form in health | ↑ immature forms (bands; IG/smear immaturity) defines left shift |
| IG fraction (analyzer) | Not counted as IG | Bands are mature-stage; IG parameter is promyelocyte–metamyelocyte on most analyzers |
Neutrophil pattern comparison
| Pattern | ANC / WBC | Smear | Favors |
|---|---|---|---|
| Reactive triad | ↑ WBC, ↑ ANC | Toxic granulation, ↑ bands | Acute infection/inflammation |
| Steroid effect | ↑ ANC | Often unremarkable | Demargination |
| MPN | Persistent ↑ | Left shift, basophilia, no toxic changes | Myeloproliferative neoplasm |
| Megaloblastic | Variable; ↓ ANC possible | Hypersegmentation | B12/folate deficiency |
Classification Frameworks
Peripheral neutrophil morphology does not define a WHO entity. WHO Classification of Haematolymphoid Tumours (5th ed.) applies when persistent neutrophilia, basophilia, and left shift suggest a myeloproliferative neoplasm rather than a reactive process.
| Relevant WHO context | Peripheral clues | Confirmatory testing |
|---|---|---|
| Chronic myeloid leukaemia (CML) | Leukocytosis, left shift, basophilia; smear may show myelocyte bulge | BCR-ABL1; hematopathology, morphology supports, does not replace molecular workup |
| Other MPN (e.g., PV, ET) | May show neutrophilia with basophilia | JAK2/CALR/MPL; marrow morphology |
| Not applicable | Isolated reactive neutrophilia with toxic granulation | Clinical correlation; no WHO haematologic entity |
Laboratory Notes
- Report ANC on every differential where neutrophil count affects care (oncology, febrile neutropenia, critical values)
- Confirm whether band forms are included in ANC calculation per institutional protocol
- Investigate instrument flags before release; do not transmit unverified differentials when smear review is required
- Document critical-value notification time in the LIS when ANC meets critical threshold
- Hypersegmentation on smear should prompt B12/folate and related correlation, not empiric clinical treatment directives in the laboratory report
- Blast-equivalent cells on smear supersede reactive pattern assignment, hold release pending confirmation
References
Authoritative textbooks, guidelines, and reviews supporting this reference entry. Verify reference intervals, critical limits, and reflex criteria against institutional protocols and current guideline editions.
Textbooks
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Elsevier; 2021.
- Rodak BF, Carr JH. Rodak's Hematology: Clinical Principles and Applications. 6th ed. Elsevier; 2020.
- Hoffbrand AV, Moss PAH, Pettit JE. Essential Haematology. 8th ed. Wiley-Blackwell; 2019.
- McKenzie SB, Williams JL. Clinical Laboratory Hematology. 4th ed. Pearson; 2022.
Professional Monographs
- Barnes PW, McFadden SL, Machin SJ, Doig K. Laboratory Hematology Practice. Wiley-Blackwell; 2012.
CLSI and Professional Guidelines
- Clinical and Laboratory Standards Institute. Reference Leukocyte (WBC) Differential Count (Proportional) and Evaluation of Instrumental Methods; Approved Standard. CLSI document H20-A2. CLSI; 2007.
- Clinical and Laboratory Standards Institute. Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory; Approved Standard. CLSI document EP28-A3c. CLSI; 2010.
- Clinical and Laboratory Standards Institute. Management of Critical- and Significant-Risk Results. CLSI guideline GP47-Ed1. CLSI; 2015.
WHO Publications
- World Health Organization Classification of Haematolymphoid Tumours. 5th ed. Lyon: International Agency for Research on Cancer; 2022.
Peer-Reviewed Reviews
- Farkas JD. The complete blood count to diagnose septic shock. J Thorac Dis. 2020;12(Suppl 1):S16-S21. doi:10.21037/jtd.2019.12.63
- Otieno S, Altahan A, Karri S, Kaweeta F, Lands L, Weir AB. CIN or not: An approach to the evaluation and management of chronic idiopathic neutrophilia. Blood Rev. 2021;46:100739. doi:10.1016/j.blre.2020.100739
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