Biomarker: F033-IgE Orange

Overview

F033-IgE Orange measures immunoglobulin E (IgE) antibodies directed against orange (Citrus sinensis) proteins. IgE is an antibody involved in immediate-type allergic reactions, and elevated orange-specific IgE indicates immune sensitization to orange. A positive result does not by itself confirm a clinically relevant orange allergy or predict reaction severity; results must be interpreted with the patient’s symptoms and exposure history, and an oral food challenge may be required for confirmation. Orange contains several recognized allergenic proteins, including Cit s 1, Cit s 2, Cit s 3, and Cit s 7. The test is clinically useful for evaluating suspected IgE-mediated reactions to orange and identifying sensitization when interpreted as part of an allergy assessment.

Clinical Use Cases

Evaluate suspected immediate allergic reactions after eating orange or drinking orange juice.
Support assessment of symptoms such as oral itching, urticaria, angioedema, vomiting, wheezing, or anaphylaxis associated with orange exposure.
Identify sensitization to orange in patients with a relevant clinical history.
Support evaluation of possible cross-reactivity involving citrus fruits, pollens, profilins, lipid-transfer proteins, or other plant-food allergens.
Help guide decisions about further evaluation, including supervised oral food challenge, when the diagnosis remains uncertain.
Contribute to clinical or epidemiologic research on orange allergens and IgE-mediated food allergy.

Specimen Types

Serum from venous blood.
Plasma may be accepted by some assay systems, depending on laboratory validation.
Whole blood is generally collected initially, with serum or plasma used for the assay.

Measurement Methods

Fluorescence enzyme immunoassay or other automated immunoassay for allergen-specific IgE.
Enzyme-linked immunosorbent assay (ELISA), primarily in research settings.
Radioallergosorbent testing (RAST), an older specific-IgE methodology.
Immunoblotting or component-specific IgE assays for research characterization of orange allergens such as Cit s 1, Cit s 2, Cit s 3, and Cit s 7.
Results are commonly reported in kUA/L or equivalent specific-IgE units, with laboratory-defined classes or interpretive categories.

Test Preparation and Influencing Factors

Fasting is generally not required for a standard allergy blood test.
Tell the healthcare provider about all medications, supplements, and medical conditions before testing.
Do not stop prescribed medications unless specifically instructed by a healthcare professional.
Antihistamines can suppress skin-prick test reactions, but standard serum-specific IgE testing measures circulating antibodies and is generally less affected by antihistamine use.
Recent exposure to orange does not generally require a waiting period before blood collection, although collection timing may be considered when interpreting changing clinical symptoms.
Total IgE concentration, age, atopic conditions, and assay-specific reference ranges can influence interpretation.
A positive result indicates sensitization and does not establish clinical allergy, reaction severity, or the amount of orange required to cause symptoms.
Cross-reactive IgE antibodies may contribute to a positive result without clinically significant allergy to orange.
Test interpretation should be based on a compatible clinical history; an oral food challenge is the reference method when confirmation is needed.