Shellfish allergy tests lack standardization and may be fatal

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Shellfish allergy tests lack standardization and may be fatal

Shellfish allergy tests lack standardization and may be fatal.

A new study found that the content of commercial extracts used to detect shellfish allergy varies greatly among different manufacturers. The researchers called for standardization of these extracts to avoid false negative results and protect the health of allergic patients worldwide. Shellfish allergy is the most common food allergy in adults and one of the most common food allergies in children.

Globally, shellfish allergy affects up to 3% of the population, but it is especially prevalent in Asian countries where shellfish consumption is high. Shellfish allergy usually lasts for life and can trigger anaphylaxis, a severe and potentially fatal allergic reaction.

Shellfish allergy tests lack standardization and may be fatal

Most people who are allergic to one type of shellfish (whether it is shrimp, lobster, crab, or oyster) are also allergic to other types of shellfish. Skin prick test (SPT) is the preferred method to determine food allergy. It is safe for most patients, including infants, and provides quick results.

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However, a new study led by researchers from James Cook University’s Australian Institute of Tropical Health and Medicine (AITHM) and the Tropical Futures Institute (TFI) in Singapore found that not all commercial shellfish allergy SPTs are the same.

“SPT is usually the preferred first-line diagnostic method,” said Dianne Campbell, one of the co-authors of the study. “If you are allergic to the allergen, you will develop a small itchy swelling and redness on your skin within 10-15 minutes.”

Commercial allergen extracts are produced specifically for SPT. They are solutions of proteins extracted from relevant allergenic substances, plus glycerol as a preservative. Due to differences in source materials, preparation methods, or allergen preparation techniques, different manufacturers may produce different amounts and proportions of major allergenic proteins for the same allergen.

In 2019, the researchers evaluated 26 commercial fish allergen extracts for SPT and found large variations in allergen content. In some extracts, the major fish allergens were not detectable. This time, they studied the extracts used to detect shellfish allergy.

Andreas Lopata, one of the co-corresponding authors of the study, said: “In the current study, we used biochemical and immunological methods as well as mass spectrometry to test 11 commercial crustacean and 5 mollusk SPT extracts and found even greater and critical differences in their reliability.”

The extracts came from manufacturers in the US, Spain, and Switzerland. The researchers found that the total protein content of five shrimp (from at least three different species), four crab, two lobster, two oyster, and three clam/scallop extracts from six different manufacturers varied by up to 14-fold.

They concluded that some SPT extracts lack sufficient quantity and diversity of important shellfish allergens, which means that false negative results may occur, potentially endangering lives. Based on this study and their 2019 study, the researchers called for global standardization of allergen extracts.

Thimo Ruethers, the lead author of the study, said: “There is an urgent need for standardization of allergen extracts to improve the accuracy and reliability of SPT. In addition, improving blood tests and using region-specific allergen extracts with known amounts of clinically well-characterized allergen components are essential for significantly improving allergy testing.”

Allergen-specific IgE blood tests are very useful when skin testing is not possible or results are uncertain. Blood samples are collected and then measured in a laboratory for immunoglobulins (allergen-specific IgE) associated with allergic reactions.

The issue of standardization of allergen products, including extracts, has been discussed for years since the establishment of the WHO/IUIS Allergen Standardization Subcommittee in 1980. Despite this, allergen standardization has not been achieved in the US and Europe.

The study was published in Allergy journal, which produced the following video introducing the findings of the study and their importance in diagnosing shellfish allergy.