Reference Range

Normal findings

Eosinophils (differential count): 1-4%^[1]

Eosinophil blood count (absolute): 50-500/mm³^[1]

Interpretation

Increased eosinophil count (eosinophilia) may occur in many disease states, including but not limited to the following conditions:

Allergies
Dermatologic disorders
Parasitic infections
Bacterial infections
Myeloproliferative disorders and other malignancies
Collagen-vascular diseases
Side effects of medications

Eosinophil-associated diseases occur in all epithelial organs, including the gastrointestinal tract, urinary tract, upper and lower respiratory tracts, the skin, and the heart.

An absolute eosinophil count greater than or equal to 5x10⁹/L indicates hypereosinophilia.

Esophageal biopsy demonstrating more than 20 epithelial eosinophils per high-power field indicates eosinophilic esophagitis.

Eosinophilic vasculitis is indicated by angiocentric eosinophil major basic protein (eMBP) staining.

Skin biopsy demonstrating few to many intact eosinophils indicates eosinophil-associated skin disease. Biopsy staining typically reveals extracellular eMBP, often out of proportion to the numbers of intact eosinophils.

Collection and Panels

See the list below:

Specimen: Blood
Container: Lavender (EDTA) or pink (K₂ EDTA) and unstained whole blood smears.
Collection method: Venipuncture

Laboratory tests for nasal, nasopharyngeal, sputum, and tissue specimens are also available. Discuss collection methods and requirements with your laboratory prior to collecting the specimen.

Panels

Eosinophil count is typically part of the following panels:

White blood cell count
White blood cell count with differential

Description

Eosinophils are white blood cells that play a role in fighting parasitic, viral, and bacterial infections. They also have a role in many other disease states (see Interpretation). Of note, however, patients without eosinophils, in the case of immunodeﬁciency or as a result of immunoglobulin G–mediated eosinophil precursor destruction, do not demonstrate any significant abnormalities related to low or absent eosinophil levels.^[2]This is notedly distinct from a deficiency of other cell lines. Additionally, this finding should be tempered by assumption, as limited case reports are available to substantiate this claim. Eosinophil-deficient eosinophils were named such because they are “acid loving” and stain positive for coal tar dyes and turn red after staining with a red dye (the Romanowsky method).

The intracellular granules contain many mediators that concentrate the stain. During cellular activation, these granules are released, resulting in toxicity to the infectious organism and/or surrounding tissue. Eosinophils may be naturally found in the thymus, gastrointestinal tract, spleen, lymph nodes, ovaries, and uterus.^[3]They are not normally found in the skin, lungs, or esophagus. Their presence in these locations may result in serious inflammatory conditions, organ injury, and disease states (see Interpretation).^{[4, 5]}

Indications/applications

The eosinophil count should be taken into consideration when determining the possible role and/or manifestation of eosinophils in the infectious or inflammatory states as follows^[5]: