Eosinophil Count (Absolute Eosinophil count)
- Whole blood (EDTA ) is needed.
- Heparinized blood can also be used.
- The absolute count should be done within 4 hours or refrigerate the sample but do count within 24 hours.
- Eosinophils count is done to diagnose allergic conditions.
- To diagnose parasite infestation and its severity.
- This can be used to monitor the treatment of parasites.
- If eosinophil count is elevated >1.5 x 109/L for over 6 months and associated with tissue damage then the hypereosinophilic syndrome is diagnosed.
- The heart valves, skin, and lungs may be affected.
- These diseases are usually treated with steroids or cytotoxic drugs.
- In case if there is a clonal cytogenetic abnormality is present in the bone marrow, it is then called chronic eosinophilic leukemia.
- Eosinophilic development:
- Eosinophils have the same stages of maturation as other white cells have. like myelocytes, metamyelocytes, band forms, and segmented stages.
- The eosinophils develop from the stem cells in the bone marrow.
- Myeloid series cells get maturation under the influence of granulocytes colony-stimulating factor (G-CSF).
- Eosinophils take 3 to 6 days in the bone marrow for the maturation, before they appear in the peripheral blood.
- Bone marrow provides a storage area for eosinophils so that these are released whenever these are needed.
- The mean transit time in the circulatory blood system is 8 hours but in some diseases has longer.
- Eosinophils migrate from the blood to tissue, like bronchial mucosa, skin, gastrointestinal tract, and vagina about 12 hours.
- Eosinophils are motile, can migrate between endothelial cells into a tissue or into an area of inflammation in the same manner as neutrophils.
- Eosinophils are like neutrophils except the cytoplasm contains orange or red staining granules.
- The blood transient time for the eosinophils is longer than the neutrophils.
- There is a diurnal variation of eosinophils count.
- the lowest count will be in the morning, 10 AM to 12 AM, and the highest level at midnight (4 am).
- Eosinophils granules contents:
- Acid phosphatase.
- Aryl sulphatase.
- Eosinophil functions:
- The eosinophils can act as phagocytic cells.
- Eosinophils are active in antigen-antibody complexes.
- Eosinophils are rich in histamine granules.
- Eosinophils take part in hypersensitivity reaction type 1.
- It helps in the detoxification process.
- A special role in the allergic reaction.
- They are defensive against the parasitic infestation.
- Eosinophils remove the fibrin during the inflammation,
- Eosinophils with the help of antibody IgE can produce histamine from the mast cells or the basophils.
- Characteristic features of eosinophils:
- Cell size 10 to 16 µm in diameter.
- The nucleus has two to three lobes. and the N:C ratio is 1:1. The nucleus is central or eccentric. The nuclear chromatin is deep-blue purple and coarsely granular chromatin.
- There are no nucleoli.
- The cytoplasm contains red, uniform, specific eosinophilic granules.
Procedure to count Eosinophils:
1. The best method to count eosinophils is an automated analyzer.
2. Dunger’s solution:
- This will use the acid dye like eosin.
- Water may be used to lyse the RBC when the eosinophils are resistant to water.
3. Phloxine stain: It consists of:
- Phloxine 0.1% solution to water 10 mL.
- Distilled water 40 mL.
- Propylene glycol 50 mL.
- Sodium carbonate 1% 1 mL.
- A sample of the blood is diluted in the WBC pipette as 1: 20 dilution with staining fluids.
- Mix well for 30 seconds.
- Now fill the chamber and count the colored eosinophils.
- Leave the chamber for at least 10 minutes to count the cells.
- Absolute value : 50 to 400 cell/cmm
- Peripheral blood smear (DLC): 1 to 5%.
- Normal bone marrow = 0 to 3%.
- Absolute count = 0 to 0.7 x 109/L
- Differential count = 0 to 3% of total WBC
Eosinophilia, Increased Eosinophil count is seen in:
- when eosinophils are more than 5 % or > 500 cells/cmm.
- Allergic disorders:
- Bronchial asthma.
- Angioneurotic edema.
- Hay fever.
- Drug sensitivity.
- Food sensitivity.
- Graft-versus-host disease.
- Skin diseases:
- Exfoliative dermatitis.
- atopic dermatitis.
- Parasitic infestations
- Especially those parasites which invade the tissue. e.g. Trichinosis, and Echinococcus, amoebiasis, hookworm, tape-worm, and ascariasis.
- Hematological disorders:
- Chronic myeloid leukemia.
- Polycythemia vera.
- Pernicious anemia.
- Hodgkin’s lymphoma.
- Hypereosinophilic syndrome:
- Eosinophilic leukemia.
- Trichinosis invasion.
- Dermatitis herpetiformis.
- Malignant tumors:
- Especially with metastasis and necrosis.
- Hodgkin’s disease.
- Clonal T-cell disorders.
- Myeloproliferative diseases including systemic mastocytosis.
- Pulmonary syndromes:
- Eosinophilic pneumonia.
- Tropical pulmonary eosinophilia.
- Loeffler’s syndrome (transient pulmonary infiltrates).
- Allergic granulomatosis.
- Loeffler’s syndrome.
- Tropical eosinophilia.
- Rheumatoid arthritis.
- Certain poison.
Eosinopenia, when < 50/cmm seen in the following conditions:
- Cushing’s syndrome.
- Due to some drugs like ACTH, epinephrine, thyroxine, and prostaglandin.
- In the shift to the left where there are immature cells.