Allergen Profile, Sesame, IgE With Component Reflex

Serum

0.8 mL

0.6 mL (Note: This volume does not allow for repeat testing.)

Gel-barrier serum separator tube

This test supports the diagnosis of sesame allergy by detection of sIgE antibodies to levels to Ses i 1.

Allergen-specific IgE assays do not demonstrate absolute positive and negative predictive values for allergic disease. Clinical history must be incorporated into the diagnostic determination. Although the use of component resolved IgE testing may enhance the evaluation of potentially allergic individuals over the use of whole extracts alone, it cannot yet replace clinical history and oral food challenge in most cases. Sensitization against thus far unidentified determinants that are not found in the whole extract or in components might cause symptoms in rare cases.

Limited, but highly variable, immunological cross-reactivity has been observed between Ses i 1 and other allergen components, such as Cor a 14 (hazelnut), Ara h 2 (peanut), Jug r 1 (English walnut), Ber e 1 (Brazil nut), Ana o 3 (Cashew nut).^1,2

Thermo Fisher ImmunoCAP® Allergen-specific IgE

Sesame is one of the oldest known cultivated oilseed plants and both the seeds and oil are commonly used ingredients in African, Asian, Mediterranean and Middle Eastern cuisine. Traditionally it is consumed as tahini paste or halva sweets, and it is also used as toppings on bread and crackers. It may be a hidden allergen in processed foods such as dips, spreads, bakery goods and cereals when added as flour, paste or oil, and it may occur unintentionally due to cross contamination during production. Sesame is a common trigger of allergic symptoms such as wheezing, dyspnea, asthma, atopic dermatitis and anaphylaxis, likely due to its widespread use in the food, pharmaceutical and cosmetic industries.^3-5 With the high risk of accidental intakes and reactions, many countries, including the US have recognized sesame as priority food allergen requiring labelling on the products.^6,7 The FASTER Act was signed into law in April of 2021 and amends the list of major food allergens that manufacturers must declare under the Food Allergen Labeling and Consumer Protection Act of 2004 ("FALCPA') to include sesame, in addition to milk, eggs, fish, shellfish, tree nuts, peanuts, wheat, and soybeans.⁷

The prevalence sesame allergy has been estimated to be between 0.1-0.2 percent in the US based on self-reported or probable diagnosis evaluated on the basis of symptoms and sensitization.⁸ Sesame allergy is considered the ninth most common childhood food allergy in the USA.³ Sesame can cause severe allergic reactions.⁹ Sesame allergy commonly co-exist with peanut and tree nut allergy, with 50-60% of patients also being allergic to peanut and/or tree nuts.^9,10 Sesame allergy is often lifelong as only about 20-30% of children outgrow their sesame allergy.³

The diagnostic assessment of allergy starts with the patient’s clinical history and examination and is followed by an extract-based analysis to confirm the presence of specific IgE (sIgE) antibody.^11,12 sIgE is necessary but not sufficient for eliciting an allergic response and thus generating a definitive diagnosis of allergic disease. Testing utilizing allergenic extracts does not lend itself to the differentiation of primary sensitization from a cross-reactivity-driven response because of the complexity of the extracts. Extracts contain most of the extractable allergenic components from the suspected sensitizer. However, it is often not possible to predict the relative risk of having a systemic allergic reaction using an extract-based diagnostic test. Component Resolved Diagnostics (CRD) refers to the use of purified or recombinant allergens in the serologic assessment of individuals who suffer reproducible hypersensitivity reactions with exposures to an allergen at a dose tolerated by non-allergic individuals.¹¹ This approach offers advantages over the use of a complete extract, especially in polysensitized individuals, given its usefulness for distinguishing between sensitizations specific to singular species and sensitizations due to cross-reactivity.¹³ Allergic sensitization to sesame may be induced not only by direct/indirect exposure but also by a cross-reaction mechanism involving some families of allergenic proteins.

Ses i 1

Ses i 1, is a major storage protein in sesame¹⁴ that is stable to heat and proteases.^1,14 As a consequence, Ses i 1 allergenicity is maintained on cooking and survives the digestive process. Measurement of sIgE to Ses i 1 performed well compared to testing with whole sesame (both sIgE and skin prick testing) in the diagnosis of sesame allergy.^2,15-20 Testing for Ses i 1 may therefore help facilitate decision when to perform sesame oral food challenge, especially in patients with high levels of specific IgE to Ses i 1 and a high probability to react.^17-19 The majority of sesame allergic patients are sensitized to Ses i 1.^14,17 Ses i 1 is also reported to be the most clinically relevant sesame allergen for laboratory identification of patients with higher likelihood of severe allergic reactions.¹⁴