Biomarker: F215-IgE Lettuce

Overview

F215-IgE Lettuce measures immunoglobulin E (IgE) antibodies in blood that recognize proteins in lettuce (Lactuca sativa). Lettuce contains several IgE-binding proteins; Lac s 1, a non-specific lipid transfer protein, has been identified as a major lettuce allergen in some patients. A positive result indicates sensitization, which may be associated with oral allergy syndrome, urticaria, gastrointestinal symptoms, respiratory symptoms, or anaphylaxis, but it does not by itself establish clinical food allergy. The test is clinically useful when interpreted with a compatible history of symptoms after lettuce exposure and may support decisions about further allergy evaluation.

Clinical Use Cases

Supports evaluation of suspected IgE-mediated lettuce allergy after symptoms associated with lettuce exposure.
Helps assess sensitization in patients with suspected oral allergy syndrome or pollen-food allergy syndrome.
May contribute to evaluation of systemic reactions, including suspected lettuce-associated anaphylaxis.
Provides an alternative or complement to skin-prick testing when skin testing is unsuitable, such as with extensive dermatitis or use of medications that interfere with skin-test results.
May be used in clinical research investigating lettuce allergens, cross-reactivity, and occupational respiratory allergy.
Helps guide, but does not replace, specialist assessment and medically supervised oral food challenge when diagnosis remains uncertain.

Specimen Types

Venous blood, typically submitted as serum.
Fresh lettuce material may be used for skin-prick or prick-to-prick testing, but it is not the specimen for F215-specific IgE measurement.

Measurement Methods

In-vitro serum allergen-specific IgE immunoassay, commonly reported in kUA/L or a comparable standardized unit.
Fluorescence enzyme immunoassay or other solid-phase immunoassay platforms using lettuce extract.
Immunoblotting and ELISA may be used in research to characterize lettuce IgE-binding proteins, but these are not generally routine clinical tests.
Component-resolved testing for individual lettuce allergens, such as Lac s 1, may be available in specialized settings or research, but F215 generally refers to an extract-based lettuce allergen measurement.

Test Preparation and Influencing Factors

Fasting is generally not required for an allergy blood test.
Most medications do not need to be stopped for serum-specific IgE testing, but the ordering clinician should review all medicines. Do not stop medication without medical advice.
Antihistamines can interfere with skin-prick testing but generally do not prevent blood-specific IgE measurement.
Results should be interpreted with the timing, amount, and form of lettuce consumed, associated symptoms, cofactors such as exercise or alcohol, and relevant pollen or food exposures.
A positive result indicates sensitization and does not prove that eating lettuce causes symptoms or predict reaction severity.
A negative result does not absolutely exclude allergy, particularly when the clinical history is strongly suggestive or the relevant allergen is insufficiently represented in the extract.
Total IgE, atopic dermatitis, cross-reactive carbohydrate determinants, assay characteristics, and differences among lettuce varieties or extracts may affect interpretation.
Testing should be selected on the basis of a focused allergy history rather than broad, indiscriminate food panels.

Synonyms

F215 lettuce-specific IgE
Lettuce allergen-specific IgE
Lettuce serum-specific IgE
Lactuca sativa-specific IgE
Anti-lettuce IgE
Lettuce IgE blood test
Lettuce RAST, an older term for allergen-specific IgE testing
Lac s 1-specific IgE, when testing the individual lipid-transfer-protein component rather than the whole lettuce extract