DIFFERENTIAL LEUCOCYTE COUNT

• Neutrophils: 50-70%
• Eosinophils: 1-4%
• Basophils: 0-1%
• Lymphocyte: 20-40%
• Monocyte: 2-8%
• Infants and children have fewer neutrophils (40-60%) and more lymphocytes (25-56%)

• Determination of percentage distribution of leucocytes in the peripheral blood is known as differential leucocyte count (DLC). Five types of leucocytes are encountered in normal peripheral blood. They are divided into Granulocytes & Agranulocytes. Neutrophils, Eosinophils and Basophils are Granulocytes and Lymphocytes & Monocytes are Agranulocytes
• DC is vital for the diagnosis of a number of blood related diseases involving leucocytes or red cells. Its primary use is to identify changes in the distribution of white cells, which may be related to a particular disease like a specific infection (e.g. typhoid) or a malignant condition (e.g. Leukemia)

Neutrophils:

• Commonest leucocytes .They constitutes 50-70% of the total leucocytes and are of two types- Segmented & band. Neutrophils normally make up the largest number of circulating WBCs. They move into an area of damaged or infected tissue, where they engulf and destroy bacteria

Eosinophils :

• Slightly larger than Neutrophils with a diameter 10-14 µm .Nucleus usually has 2 lobes (sometimes 3).It is involved in defending the body from allergic reactions. Eosinophils respond to infections caused by parasites, play a role in allergic reactions (hypersensitivity) and control the extent of immune responses and inflammation

Basophils:

• Rarest leucocytes (0.5%). The nucleus occupies a relatively greater portion of the cell. Exact function is not known. It contains heparin, histamine & slow- reacting substance. Cells are phagocytic. Basophils are involved in allergic reactions.

Monocytes:

• 2-8% of total leucocytes .These are the largest leucocytes (12-25 µm). Nucleus is large & occupies 50% of the cells. Involved in phagocytic activity and acts as the second line of defence in the body. Monocytes move to an area of infection and engulf and destroy bacteria. They are associated more often with chronic rather than acute infections.

Lymphocyte:

• 20-40% of total leucocytes, it mediates immunologic responses of the body. Lymphocytes exist in the blood and the lymphatic system. They are of 3 types-T lymphocytes, B lymphocytes and Natural killer cells.
• T lymphocyte mediates cellular immunity. Recognise foreign substances and process them for removal
• B lymphocyte is associated with humoral immunity. Produce antibodies as part of the body’s natural immune responses
• Natural killer cells directly attack and kill abnormal cells

• WBC differential count is used as a part of Complete blood count when there is s/s of infection and /or inflammation (fever, chills, body aches, pain and headache)
• To diagnose the cause of a high or low WBC count and diagnose the specific cause of an illness

Neutrophilia

Physiological

• Exercise
• Pregnancy
• Parturition
• Food intake
• Emotional stress
• Exposure to cold

Pathological

• Non-infective inflammations e.g. rheumatic fever
• Non-inflammatory conditions e.g. myocardial infarction, pulmonary embolism
• Acute haemorrhage
• Muscle trauma e.g. following surgery
• Leukemia e.g. chronic myeloid leukemia
• Toxic conditions e.g. uremia, hepatic coma
• Coricosteroid therapy
• Cushing syndrome
• Trauma
• Heart attack

Eosinophilia

Allergic conditions

• Bronchial asthma
• Urticaria
• Food allergy
• Hay fever

Parasitic infestations

• Hookworm
• Filariasis
• Hydatid disease

Skin diseases

• Psoriasis
• Pemphigus

Others

• Collagen diseases
• Periarteritis nodosa
• Hodgkin’s disease
• Addison’s disease
• Certain leukemias
• Drug Reaction
• Inflammatory diseases

Basophilia

• Chronic myeloid leukemia
• Polycythemia

Lymphocytosis

• Chronic infections - TB, Pertussis, syphilis, brucellosis
• Infectious mononucleosis
• Lymphocytic leukemia
• Lymphoma
• Viral infections
• CP
• Toxoplasmosis

Monocytosis

• Protozoan diseases - Malaria, kala azar
• Hodgkin’s disease
• Monocytic or myelomonocytic leukemia
• ACTH therapy
• Chronic Infections
• Collagen vascular diseases

Neutropenia

Physiological

• Rare, occurs after chronic exposure to severe cold.

Pathological

• Starvation and debility
• Typhoid and paratyphoid
• Aplastic Anemia
• Parasitic infections e.g. malaria, kala azar
• Viral infections e.g.: measles, influenza, viral hepatitis
• Hypersplenism
• Drug induced Neutropenia
• Auto immune disorders
• Myelodysplasia
• Bone marrow damage (Chemotherapy, Radiotherapy)

Eosinopenia

• ACTH therapy
• Cushing’s disease
• Acute pyogenic infections
• Aplastic anemia

 Basilopenia

• Rare as in severe septicaemia or aplastic anemia

 Lymphocytopenia

• Immuno-suppressive therapy
• ACTH therapy
• Hodgkin’s disease
• Bone marrow failure
• Auto immune disorders
• Infections

Monocytopenia (rare)

• Bone marrow failure
• Aplastic anemia
• Septicemia