Overview: Absolute Eosinophil Count Test
Introduction: The Absolute Eosinophil Count Test measures eosinophils, a type of white blood cell, to diagnose conditions like allergies, parasitic infections, or blood disorders, which can cause symptoms such as itching, swelling, or breathing difficulties. Following 2023 hematology guidelines, it uses flow cytometry for precise counting, aiding in identifying allergic or infectious states. This test is critical for guiding treatments like antihistamines or antiparasitic drugs, preventing complications, and improving outcomes in hematology.

Other Names: AEC Test, Eosinophil Count Assay.

FDA Status: Laboratory-developed test (LDT), meeting hematology standards for diagnostic accuracy.

Historical Milestone: Eosinophil counting began in the early 1900s with microscopy. Flow cytometry, introduced in the 1980s, improved precision, and by the 2000s, automated systems enhanced clinical utility for allergy and infection diagnostics.

Purpose: Diagnoses allergies, infections, or blood disorders, guides treatment, and monitors disease in patients with symptoms like itching or respiratory issues.

Test Parameters: 1. Absolute Eosinophil Count

Pretest Condition: No fasting required. Collect whole blood at any time. Report symptoms like itching, swelling, or recent infections, and list medications (e.g., steroids) that may affect eosinophil levels.

Specimen: 2-5 mL whole blood (EDTA tube). Transport in a biohazard bag within 24 hours at room temperature to preserve cell integrity.

Sample Stability at Room Temperature: 24 hours

Sample Stability at Refrigeration: 48 hours

Sample Stability at Frozen: Not frozen, as cells may lyse.

Medical History: Document allergic symptoms, infections, or family history of blood disorders. Include current medications, especially steroids or immunosuppressants.

Consent: Written consent required, explaining the test's purpose, diagnostic implications, and potential treatment needs.

Procedural Considerations: Uses flow cytometry to count eosinophils. Results are available in 1-2 days, enabling rapid clinical decisions.

Factors Affecting Result Accuracy: Steroids or recent infections may suppress eosinophil counts. Hemolysis or improper storage can degrade samples. Timing of collection is less critical but should avoid post-treatment periods.

Clinical Significance: Elevated eosinophil counts suggest allergies, parasitic infections, or hematologic disorders, prompting targeted therapy. Normal counts may require further testing to rule out transient suppression.

Specialist Consultation: Consult an allergist or hematologist for result interpretation. Allergy specialists are advised for persistent allergic symptoms.

Additional Supporting Tests: Allergy panel, stool ova and parasite test, or bone marrow analysis to confirm underlying causes.

Test Limitations: False lows may occur with steroid use. Non-specific eosinophilia requires clinical correlation to pinpoint causes.

References: American Society of Hematology Guidelines, 2023; Wardlaw AJ, Journal of Allergy and Clinical Immunology, 2022.