Structure and normal values of the leukocyte count
Leukocytes are a heterogeneous group of blood cells with protective functions, which includes five main types: neutrophils, lymphocytes, monocytes, eosinophils, and basophils. In a healthy adult, the levels of these elements in the blood follow strict percentage norms:
- Segmented neutrophils: 51–67%
- Band neutrophils: 3–5%
- Immature neutrophils (metamyelocytes): 0–1%
- Lymphocytes: 21–35%
- Monocytes: 4–8%
- Eosinophils: 2–4%
- Basophils: 0.5–1%
- Myelocytes are normally absent.
Leukocyte count shifts
To assess the severity of the condition and the nature of the inflammatory process, the concept of a leukocyte count shift is used:
- Shift to the left is characterized by an increase in band neutrophils, as well as the appearance of immature forms and myelocytes. This is observed in acute infections, acidosis, physical overexertion, and comatose states.
- Shift to the right is manifested by the appearance of hypersegmented neutrophils in the blood.
For an in-depth assessment, the shift index (SI) is used, which is calculated as the ratio of the sum of myelocytes, metamyelocytes, and band neutrophils to segmented neutrophils. Normally, this indicator is 0.06.
Neutrophilia and neutropenia
Quantitative changes in the neutrophil lineage play a key role in diagnosis:
- Neutrophilia (neutrophil leukocytosis) — an increase in cell levels. Causes include inflammatory processes, oncological diseases, the postoperative period, ischemic tissue necrosis (infarctions), endogenous intoxication (uremia), as well as the use of certain medications and physical exertion.
- Neutropenia — a decrease in levels. The isolated form is associated with a deficiency of precursors in the bone marrow. Absolute granulocytopenia is observed in severe infections (sepsis, pertussis), hematological pathologies, immune disorders, and after cytostatic therapy.
Lymphocytosis and lymphopenia
Changes in the lymphocytic lineage are divided into absolute and relative:
- Lymphocytosis (absolute > 3.5 × 10⁹/L, relative > 40%) often accompanies viral infections (ARVI, herpes, rubella), as well as blood disorders such as lymphocytic leukemia.
- Lymphopenia (a decrease in the number of lymphocytes) can be relative in acute infections with enhanced granulocytopoiesis. Absolute lymphopenia is characteristic of immunodeficiency states (AIDS, DiGeorge syndrome), Hodgkin's lymphoma, exposure to ionizing radiation, and corticosteroid therapy.
Briefly: answers to topical questions
What is a shift to the right of the leukocyte count and in which diseases does it occur?
A shift to the right of the leukocyte count is an increase in the number of mature segmented neutrophils, the appearance of hypersegmented forms, and a decrease or disappearance of band neutrophils. This condition indicates an adequate protective response of bone marrow hematopoiesis. It occurs in the following pathological processes:
- Infectious diseases — as a reaction to the introduction of an infectious agent.
- Inflammatory processes — indicates a favorable course of the disease.
What pathological processes lead to eosinophilia?
Eosinophilia is observed in a number of pathological processes. Sources-confirmed causes include:
- Allergic diseases — bronchial asthma, urticaria.
- Parasitic infestations.
- Infections — scarlet fever; eosinophilic lung diseases also specify parasitic infections, fungal infections (Aspergillus), bacterial infections (tuberculosis, atypical mycobacterial infection, Brucella), and viral infection caused by respiratory syncytial virus.
- Blood diseases — chronic myeloid leukemia, eosinophilic leukemia, polycythemia vera, Hodgkin's lymphoma, acute lymphoblastic leukemia.
- Malignant tumors — renal cell carcinoma.
- Idiopathic eosinophilic lung diseases — simple pulmonary eosinophilia, acute eosinophilic pneumonia, chronic eosinophilic pneumonia, hypereosinophilic syndrome.
- Drug-induced eosinophilic lung diseases — with the use of aminosalicylic acid, PAS, NSAIDs, captopril, cocaine, minocycline, nitrofurantoin, phenytoin.
- Immunological diseases — granulomatosis with polyangiitis.
- Sputum eosinophilia may occur in bronchial asthma, eosinophilic granulomatosis with polyangiitis, allergic bronchopulmonary aspergillosis, and mycoses.
In which infections and diseases is monocytosis observed?
Monocytosis is observed in a number of infectious, hematological, and toxic pathologies. The main diseases and conditions include:
- Infectious diseases — infectious mononucleosis, rubella, malaria, and other infectious diseases (cause slight monocytosis).
- Hematological and oncological diseases — histiocytosis, myelodysplastic syndrome, monocytic leukemia, myeloid leukemia, Hodgkin's lymphoma.
- Iatrogenic factors and poisonings — intake of certain medications (griseofulvin, haloperidol) and poisonings with chemical substances (phosphorus, tetrachloroethane).
A shift to the left means "young" cells (myelocytes, immature forms, bands) rush to the rescue in acute inflammation. A shift to the right means "old" hypersegmented neutrophils.
Class and exam questions
What is a left shift of the leukocyte formula?
This is an increase in the number of band neutrophils and the appearance of less mature forms (metamyelocytes and myelocytes), which is observed in acute infections, acidosis, and physical overexertion.
What causes absolute granulocytopenia?
It is observed in severe infectious-toxic processes and sepsis, hematological diseases (acute leukemia, panmyelopathy), immune disorders, and after cytostatic therapy.
What is the difference between absolute and relative lymphocytosis?
Absolute lymphocytosis is an increase in the total lymphocyte count above 3.5 × 10⁹/L, and relative lymphocytosis is when their share exceeds 40% in the standard leukocyte count.
What else to study on this topic
- Eosinophilia and its diagnostic significance in parasites and allergies
- Pathogenesis and causes of monocytosis and monocytopenia
- Criteria and diagnosis of basophilia and basopenia
- Etiology and risk factors for the development of leukemias
- Molecular mechanisms of malignant transformation and the role of the Philadelphia chromosome
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