Eosinophil Count

What Sample is needed for Eosinophil Count?

1. Whole blood (EDTA) is needed.
2. Heparinized blood can also be used.
3. The absolute count should be done within 4 hours, or refrigerate the sample, but do count within 24 hours.

What are the Indications for Eosinophil Count?

1. An eosinophil count is done to diagnose allergic conditions.
2. To diagnose parasite infestation and its severity.
3. This can be used to monitor the treatment of parasites.

What Factors affect the eosinophil count?

1. The daily eosinophil count is lowest in the morning. Then, there is a rise from noon until midnight (repeat eosinophil counts each day simultaneously).
2. There is a decreased count in stress, burns, postoperative state, labor, and electroshock.
3. Eosinophils decrease after the administration of corticosteroids.

How will you define absolute Eosinophil Count?

1. Absolute eosinophil count is a blood test that measures one type of blood cell called eosinophils.
2. Eosinophiluria is defined when urinary eosinophils are >1% as eosinophils.
3. Eosinophils are of two types:
   1. Eosinophils in peripheral blood smear.
   2. Tissue eosinophils. Eosinophils migrate to bronchial mucosa, skin, GIT, and vagina in about 12 days.

What are important facts about Eosinophils?

1. Hypereosinophilic syndrome is diagnosed if the eosinophil count is elevated >1.5 x 10⁹/L  for over 6 months and is associated with tissue damage.
2. Persistent eosinophilia with eosinophilic infiltration leads to tissue damage and organ dysfunction.
   1. The heart valves, skin, and lungs may be affected.
   2. These diseases are usually treated with steroids or cytotoxic drugs.
3. If a clonal cytogenetic abnormality is present in the bone marrow, it is called chronic eosinophilic leukemia.

How will you describe eosinophil development?

1. Eosinophils have the same stages of maturation as other white cells, like myelocytes, metamyelocytes, band forms, and segmented stages.
2. The eosinophils develop from the stem cells in the bone marrow.
3. Myeloid series cells mature under the influence of granulocyte colony-stimulating factor (G-CSF).
4. Eosinophils take 3 to 6 days in the bone marrow for maturation before they appear in the peripheral blood.
5. Bone marrow provides a storage area for eosinophils to be released whenever needed.
6. The mean transit time in the circulatory blood system is 8 hours, but in some diseases, it is longer.
7. Eosinophils migrate from the blood to tissue after about 8 hours, like bronchial mucosa, skin, gastrointestinal tract,  and vagina, for about 12 hours.
8. Eosinophils are motile and can migrate between endothelial cells into a tissue or an area of inflammation like neutrophils.

Eosinophil maturation in the bone marrow

What is the structure of eosinophils?

1. Eosinophils are slightly larger than neutrophils. Cell size 10 to 16 µm in diameter.
2. The nucleus has two to three lobes. The N: C ratio is 1:1. The nucleus is central or eccentric. The nuclear chromatin is deep-blue purple and coarsely granular chromatin.
3. The nuclei have two lobes and occasionally three.
4. There are no nucleoli.
5. The cytoplasm contains red, uniform, specific eosinophilic granules and occasional vacuoles.
6. Eosinophils are like neutrophils, except the cytoplasm contains orange or red staining granules.
7. The blood transient time for the eosinophils is longer than for the neutrophils.
8. There is a diurnal variation of eosinophil count.
   1. The lowest count will be in the morning, from 10 AM to 12 AM, and the highest at midnight (4 am).
9. The specific granules of eosinophils contain:
   1. Major basic proteins.
   2. Peroxidase.
   3. Perforins.
   4. Membrane damaging substances.

Name the Eosinophil’s granules?

These are hydrolytic enzymes:

1. Peroxidase.
2. Acid phosphatase.
3. Aryl sulphatase.
4. β-glucuronidase.
5. Phospholipase.
6. Cathepsin.
7. Ribonuclease.

 But eosinophils lack:

1. Cationic proteins.
2. Lysosomes.
3. Alkaline phosphatase.

What are the functions of Eosinophils?

1. The eosinophils can act as phagocytic cells.
2. Eosinophils are mainly present in the skin, gastrointestinal tract, and lungs which are involved in hypersensitivity reactions (Type 1) like asthma, hay fever, and eczema.
3. Eosinophils are active in antigen-antibody complexes.
4. Eosinophils are rich in histamine granules.
5. Eosinophils take part in hypersensitivity reaction type 1.
6. It helps in the detoxification process.
7. A special role in the allergic reaction.
8. They are defensive against parasitic infestation. There is the production of IgG and IgE antibodies.
   1. Eosinophils bind to the antibody-coated parasites and release cytotoxic substances that damage the parasites’ surface, destroying them.
   2. Antibody-dependent cell-mediated cytotoxicity by eosinophils is effective against parasites in the tissue. This immune response protects from schistosomiasis, hookworms, Ascaris, Fasciola, and Toxocara.

Eosinophil role in the destruction of the parasite (ADCC)

9. Eosinophils remove the fibrin during the inflammation,
10. With the help of the IgE antibody, Eosinophils can produce histamine from the mast cells or the basophils.
11. Eosinophils contain substances that inactivate histamine and factors released during an anaphylactic reaction.

Eosinophil morphology

How will you count Eosinophils?

• 1. The best method to count eosinophils is an automated analyzer.

Dunger’s solution:

1. This will use an acid dye like eosin.
2. Water may be used to lyse the RBC when the eosinophils resist water.

Phloxine stain: It consists of:

1. Phloxine 0.1% solution to water 10 mL.
2. Distilled water 40 mL.
3. Propylene glycol  50 mL.
4. Sodium carbonate 1%  1 mL.

What is the procedure for Eosinophil Count?

1. A blood sample is diluted in the WBC pipette as 1: 20 dilutions with staining fluids.
2. Mix well for 30 seconds.
3. Leave the chamber for at least 10 minutes to count the cells.
4. Now, fill the chamber and count the colored eosinophils.

What is the normal Eosinophil Count in blood?

Source 2

1. Absolute value =  50 to 400 cells/cmm
2. Peripheral blood smear (DLC) =  1% to 5%.
3. Normal bone marrow = 0% to 3%.

Source 4

1. Absolute count = 0% to 0.7 x 10⁹/L
2. Differential count = 0% to 3% of total WBC

What are the conditions when Eosinophils are Increased?

1. When eosinophils are more than 5% or >500 cells/cmm.
2. Allergic disorders:
   1. Bronchial asthma.
   2. Angioneurotic edema.
   3. Hay fever.
   4. Drug sensitivity.
   5. Food sensitivity.
3. Graft-versus-host disease.
4. Bacterial infection in some conditions may be associated with eosinophilia like:
   1. Scarlet fever.
   2. Brucellosis.
5. Skin diseases:
   1. Eczema
   2. Exfoliative dermatitis.
   3. Pemphigus.
   4. Psoriasis.
   5. Urticaria.
   6. Angioedema.
   7. Atopic dermatitis.
6. Parasitic infestations:
   1. Especially those parasites that invade the tissue. e.g., Trichinosis, Echinococcus, amoebiasis, hookworm, tape-worm, and ascariasis.
7. Hematological disorders:
   1. Chronic myeloid leukemia.
   2. Polycythemia vera.
   3. Pernicious anemia.
   4. Hodgkin’s lymphoma.
8. Hypereosinophilic syndrome:
   1. Eosinophilic leukemia.
   2. Trichinosis invasion.
   3. Dermatitis herpetiformis.
   4. Idiopathic.
9. Malignant tumors:
   1. Especially with metastasis and necrosis.
   2. Hodgkin’s disease.
   3. Clonal T-cell disorders.
   4. Myeloproliferative diseases include systemic mastocytosis.
10. Pulmonary syndromes:
    1. Eosinophilic pneumonia.
    2. Tropical pulmonary eosinophilia.
    3. Loeffler’s syndrome (transient pulmonary infiltrates).
    4. Allergic granulomatosis.
11. Miscellaneous:
    1. Loeffler’s syndrome.
    2. Tropical eosinophilia.
    3. Radiation.
    4. Rheumatoid arthritis.
    5. Tuberculosis.
    6. Sarcoidosis.
    7. Certain poison.

Hypereosinophilic syndrome:

1. Hypereosinophilic syndrome is diagnosed if the eosinophil count is elevated >1.5 x 109/L for over 6 months and is associated with tissue damage.
2. The heart valves, skin, and lungs may be affected.
3. The treatment is usually steroids or cytotoxic drugs.
4. Idiopathic.
5. Eosinophilic leukemia.
   1. Chronic eosinophilic leukemia is a clonal cytogenetic abnormality in the bone marrow.
6. Dermatitis herpetiformis.
7. Trichinosis invasion.

How will you define Eosinopenia?

1. When < 50/cmm is seen in the following conditions:
   1. Cushing’s syndrome (<50/cmm)
   2. Due to some drugs like ACTH, epinephrine, thyroxine, and prostaglandin.
   3. In the shift to the left, there are immature cells.

When can you see Eosinophilic myelocytes?

• These are found in leukemia or leukemoid blood smear.

Questions and answers: