Biomarker: F338-IgE Scallop

Overview

Scallop is an edible marine molluscan shellfish belonging to the bivalve group. Scallop proteins can trigger IgE-mediated sensitization and allergic reactions after ingestion, with tropomyosin identified as a major molluscan shellfish allergen in human studies. Exposure most commonly occurs through eating raw or cooked scallop, although occupational or environmental contact may also be relevant in some settings. Measurement of scallop-specific IgE in serum can help evaluate sensitization when interpreted with the exposure history and clinical symptoms, but a positive result alone does not establish clinical allergy.

Clinical Use Cases

Evaluation of suspected IgE-mediated scallop allergy: Supports assessment of patients who develop urticaria, angioedema, gastrointestinal symptoms, respiratory symptoms, or anaphylaxis after scallop exposure.
Serum-specific IgE assessment: Measures IgE antibodies directed against scallop proteins in a blood sample and may help identify sensitization.
Correlation with clinical history: Helps determine whether sensitization is consistent with symptoms occurring after scallop ingestion or contact.
Assessment of shellfish sensitization patterns: May be performed alongside testing to other molluscan and crustacean shellfish when reactions involve multiple seafood sources.
Evaluation of cross-reactive sensitization: Can help investigate whether scallop-specific IgE reflects recognition of shared shellfish proteins, particularly tropomyosin.
Support for further diagnostic evaluation: Results may be considered with skin-prick testing and, when clinically appropriate and medically supervised, an oral food challenge. Food challenges remain the reference approach for confirming or excluding clinical food allergy when the diagnosis is uncertain.

Specimen Types

Serum: Commonly used for measurement of scallop-specific IgE.
Plasma or blood: May be accepted by some validated laboratory methods for allergen-specific IgE measurement, depending on the assay.

Measurement Methods

Allergen-specific IgE testing: Serum or blood is tested for IgE antibodies that bind scallop extract, reported as a quantitative concentration or categorical result. The result indicates sensitization and must be interpreted with clinical history.
Component-resolved diagnostics: Measures IgE against individual allergenic proteins rather than only a whole-food extract. Tropomyosin is a clinically relevant molluscan shellfish component, although component testing is more established for some shellfish species than for scallop-specific components.
Skin-prick testing: May be used as an adjunct to serum-specific IgE testing, using commercial extracts or, in specialist settings, fresh food material. It assesses cutaneous reactivity rather than directly confirming that ingestion causes symptoms.
Oral food challenge: A medically supervised controlled exposure may be used when the history and sensitization tests do not establish whether scallop can be tolerated. It is not a blood-based measurement and carries a risk of an allergic reaction.

Test Preparation and Influencing Factors

Fasting: Fasting is generally not required for serum-specific IgE testing unless other tests collected at the same time require it.
Medications: Most medications do not prevent blood-specific IgE measurement. Medications that suppress skin responses, particularly antihistamines, are more relevant to skin-prick testing than to blood testing.
Clinical timing: Testing is interpreted in relation to the timing and circumstances of the suspected reaction. A recent exposure is not required for serum-specific IgE testing.
Total IgE concentration: High or low total IgE may affect interpretation of quantitative allergen-specific IgE results, particularly when values are low or borderline.
Age and clinical context: Allergen-specific IgE concentrations vary with age and do not independently predict the presence or severity of clinical reactions.
Cross-reactive sensitization: IgE binding to shared proteins, especially tropomyosin, may produce positive results to several shellfish species without proving that each species causes symptoms.
Sensitization versus allergy: A detectable scallop-specific IgE result demonstrates immunologic sensitization, not necessarily symptomatic allergy. Interpretation requires a compatible history and, when necessary, additional evaluation.
Assay limitations: Results can vary with the allergen extract, component composition, analytical platform, reporting units, and laboratory cutoff. A low or undetectable result also does not completely exclude clinical allergy when the history is strongly suggestive.

Cross-Reactivity

Tropomyosin: Tropomyosin is a major molluscan shellfish allergen and has been shown to bind IgE from people with shellfish allergy, including reactivity to scallop tropomyosin.
Molluscan shellfish: Structural similarity among tropomyosins may contribute to IgE cross-reactivity between scallop and other mollusks such as mussels, oysters, abalone, and squid.
Crustacean shellfish: Cross-reactive IgE recognition may also occur between mollusks and crustaceans such as shrimp, crab, and lobster because tropomyosin is shared across these groups.
Clinical relevance: Immunologic cross-reactivity does not prove that a person will react clinically to every cross-reactive shellfish. Each species should be considered in relation to the patient’s exposure history and, when appropriate, supervised diagnostic testing.
Component interpretation: Detection of IgE to tropomyosin may explain broad shellfish sensitization, but scallop-specific whole-extract IgE and component results should not be treated as equivalent to confirmed cross-allergy.

Synonyms

Common name: Scallop
Scientific name:Chlamys nobilis is a scallop species used in human allergen research.
Alternative scientific name:Mimachlamys nobilis has also been used for the scallop associated with the allergen designation Mim n 1.
Allergen designation: F338, scallop
Major identified allergen: Mim n 1, a tropomyosin allergen associated with Mimachlamys nobilis.