Biomarker: F018-IgE Brazil Nut

Overview

F018-IgE Brazil Nut measures immunoglobulin E (IgE) antibodies directed against Brazil nut proteins in a blood sample. IgE is an antibody involved in immediate hypersensitivity reactions, including food allergy. A detectable or elevated result indicates sensitization to Brazil nut but does not by itself confirm clinical allergy or predict reaction severity. The test is clinically useful when interpreted with the patient’s reaction history and, when necessary, supervised oral food-challenge findings.

Clinical Use Cases

Supports evaluation of suspected IgE-mediated Brazil nut allergy.
Helps identify sensitization in patients with a history of immediate symptoms after Brazil nut exposure.
May support assessment of possible cross-sensitization among tree nuts.
Can be used when skin-prick testing is unsuitable, unavailable, or affected by medications.
May be used as part of follow-up evaluation by an allergy specialist, although changes in specific IgE do not independently establish tolerance or allergy resolution.
Helps determine whether additional component testing, such as IgE to the Brazil nut allergen Ber e 1, may be clinically relevant. Ber e 1 is a major Brazil nut allergen associated with clinical reactions in human studies.

Specimen Types

Serum, collected from venous blood.
Plasma may be accepted by some laboratory methods, depending on the assay.

Measurement Methods

In vitro allergen-specific IgE immunoassay using Brazil nut extract.
Fluorescence enzyme immunoassay or other automated solid-phase immunoassays.
Component-resolved testing for specific Brazil nut proteins, particularly Ber e 1, when available.
Results are commonly reported as an allergen-specific IgE concentration, often in kUA/L, with assay-specific analytical classes or reference categories.

Test Preparation and Influencing Factors

Fasting is generally not required for serum-specific IgE testing.
Antihistamines usually do not need to be stopped for a blood test, unlike some skin-prick tests. Medication changes should be discussed with the treating clinician.
Testing should be ordered for foods suspected from the clinical history rather than as an unrestricted screening panel.
A positive result indicates sensitization and may occur without symptoms after eating Brazil nut.
The concentration of Brazil nut-specific IgE does not reliably predict the severity of a future reaction.
A negative result reduces the likelihood of sensitization but does not completely exclude clinically relevant allergy.
Total IgE levels, age, atopic disease, assay characteristics, and the timing of testing may influence interpretation.
Results should be interpreted with the type, timing, reproducibility, and severity of symptoms after exposure.
When history and testing remain inconclusive, a medically supervised oral food challenge may be required for diagnosis.