Biomarker: F208-IgE Lemon

Overview

F208-IgE Lemon measures serum immunoglobulin E (IgE) antibodies directed against lemon (Citrus limon) proteins. IgE is involved in immediate hypersensitivity reactions, including food-allergic symptoms. A detectable or elevated result indicates sensitization to lemon but does not by itself confirm clinical allergy, predict reaction severity, or establish that lemon caused a person’s symptoms. The test is clinically useful when interpreted with the patient’s history and, when appropriate, skin testing or a medically supervised oral food challenge.

Clinical Use Cases

Evaluation of suspected immediate hypersensitivity reactions after eating lemon or lemon-containing foods.
Assessment of possible citrus-fruit allergy in patients with symptoms such as oral itching, hives, gastrointestinal symptoms, wheezing, or anaphylaxis.
Supporting evaluation when skin-prick testing is unsuitable, unavailable, or affected by medications or skin disease.
Investigation of possible cross-reactive sensitization involving citrus, pollen, or other plant-food allergens.
Monitoring sensitization as part of an allergist-directed evaluation, recognizing that serial values do not independently establish tolerance or reaction severity.

Specimen Types

Venous blood, typically submitted as serum.
Capillary blood may be used by some validated laboratory systems, but specimen requirements are method-specific.

Measurement Methods

Allergen-specific serum IgE immunoassay.
Fluorescence enzyme immunoassay, including ImmunoCAP-type methods.
Enzyme-linked immunosorbent assay or other validated solid-phase immunoassays.
Older radioallergosorbent test methods, commonly called RAST, are historical rather than the usual current approach.

Test Preparation and Influencing Factors

Fasting is generally not required for a serum-specific IgE test.
Antihistamines usually do not interfere with blood testing in the same way they can interfere with skin-prick testing, but all medications and supplements should be reported to the ordering clinician.
Do not stop prescription or nonprescription medication unless instructed by a healthcare professional.
Results should be interpreted with the timing, amount, and form of lemon exposure and the associated symptoms.
A positive result indicates sensitization, not necessarily symptomatic food allergy; cross-reactive IgE can produce false-positive results.
The concentration of lemon-specific IgE does not reliably predict the severity of a future reaction.
Total IgE elevation, smoking, parasitic infection, and other allergic conditions may complicate interpretation of IgE results.
Reference ranges, reporting units, and positivity thresholds vary by assay and laboratory. Published clinical studies have used thresholds such as (0.35\ \mathrm{kU/L}), but laboratory-specific interpretation is required.
Oral food challenges must be performed only under qualified medical supervision because severe reactions can occur.