Absolute Eosinophilic Count(AEC)

Overview

Absolute Eosinophilic Count (AEC) is a hematological test used to measure the number of eosinophils per microliter of blood, providing essential insights into immune responses. Eosinophils are a type of white blood cell containing bilobed nuclei and cytoplasmic granules that stain bright pink or orange with eosinophilic dyes. These granules are rich in proteins and enzymes such as eosinophil peroxidase and eosinophil-derived neurotoxin, which play a critical role in fighting parasitic infections and mediating allergic reactions. AEC testing is commonly indicated in cases of asthma, drug reactions, lung diseases, allergic conditions, and parasitic infections. Normal ranges vary by age: infants (100–1000 cells/µL), children (200–1000 cells/µL), and adults (<400 cells/µL). Values beyond these ranges may indicate eosinophilia or eosinopenia, both of which have clinical significance.

Symptoms

(Clinical indicators prompting AEC testing)

1. Allergic manifestations: sneezing, nasal congestion, itchy eyes, and skin rashes.
2. Respiratory symptoms: wheezing, shortness of breath, and recurrent asthma attacks.
3. Parasitic infections: gastrointestinal disturbances, abdominal pain, diarrhea, or unexplained weight loss.
4. Systemic features: fatigue, fever, and malaise in chronic eosinophilic disorders.
5. Skin changes: urticaria, eczema, and psoriasis.
6. Hematological signs: abnormal white blood cell count on routine tests, prompting detailed eosinophil analysis.

Causes

(Underlying factors affecting eosinophil count)

1. Eosinophilia (high AEC levels):
   1. Mild (700–1500/µL): allergic rhinitis, extrinsic asthma, mild drug reactions, long-term dialysis, immunodeficiency.
   1. Moderate (1500–5000/µL): parasitic infections, intrinsic asthma, pulmonary eosinophilia syndrome.
   1. Severe (>5000/µL): parasitic diseases like Trichinella, hookworm, Toxocara canis; eosinophilic leukemia; severe drug reactions.
   1. Other causes: systemic autoimmune conditions (rheumatoid arthritis, lupus, Crohn’s disease, ulcerative colitis), psoriasis, malignant disease, and hypereosinophilic syndrome.
2. Eosinopenia (low AEC levels):
   1. Increased circulating steroids (endogenous, e.g., Cushing’s syndrome, or exogenous use).
   1. Acute bacterial infections.
   1. Elevated levels of ACTH, epinephrine, or thyroxine.
   1. Certain drug therapies leading to reduced eosinophil counts.

Risk factors

(Groups more likely to show altered AEC levels)

1. Individuals with a history of allergies: including asthma, hay fever, or atopic dermatitis.
2. Patients in parasite-endemic areas, particularly with poor sanitation or contaminated food/water sources.
3. People with autoimmune or inflammatory conditions, such as lupus, Crohn’s disease, or ulcerative colitis.
4. Patients on long-term steroid therapy, which may suppress eosinophil counts.
5. Individuals undergoing dialysis, due to immune system dysregulation.
6. Cancer patients, especially those with hematological malignancies like eosinophilic leukemia.
7. Children and infants, who are more prone to parasitic infections and allergic disorders.

Prevention

(Strategies to maintain balanced eosinophil levels and ensure accurate testing)

1. Parasitic infection control: practice good hygiene, wash hands regularly, and avoid consumption of contaminated food or water.
2. Allergy management: minimize exposure to known allergens such as pollen, dust, and pet dander; use prescribed antihistamines or inhalers for asthma.
3. Safe medication use: avoid unnecessary drug intake and monitor for eosinophil-related side effects during long-term treatments.
4. Immune health monitoring: individuals with autoimmune or chronic inflammatory diseases should undergo periodic blood tests for early detection of abnormal AEC levels.
5. Proper sample collection: collect 2–3 mL of blood in EDTA (lavender cap) or heparin (green cap) tubes, mix well, and transport immediately to the lab or store at 2–8 °C. Finger prick samples may be used for smears but are less reliable for precise counts.
6. Accurate laboratory methods: use automated blood cell counters for precise measurements; manual Neubauer chamber methods can also be applied when necessary.
7. Clinical correlation: always interpret AEC results in conjunction with patient history, symptoms, and other hematological findings.