Researchers from the Chinese University of Hong Kong have developed a more accurate test to diagnose shrimp allergies, which affect one in every 100 primary school students.
The results proved that using the basophil activation test on individual blood samples achieves a sensitivity and specificity far superior to that of other conventional allergy tests.
The test will analyze the cellular response of basophils - a type of white blood cell - in the patient's blood sample using a flow cytometer.
Currently, there are several ways to detect a shrimp allergy, including skin prick tests and measurement of the blood level of shrimp-specific IgE antibodies, but researchers said many patients have been misdiagnosed under these methods.
The gold standard for shrimp allergy diagnosis is a "double-blinded, placebo-controlled food challenge," in which patients receive increasing doses of the suspected food allergen and a placebo. But this method also has its limitations as it is risky, labor-intensive and expensive, the team said.
The study recruited 35 patients who exhibited on at least two occasions immediate allergic reactions after eating shrimp. Fifteen of them were confirmed to be allergic to shrimp while the remaining 20 participants were tolerant of it.
All patients underwent the skin prick test, measurement of shrimp-specific IgE and BAT.
While the skin prick tests and shrimp-specific IgE measurements showed higher sensitivity at 93 percent compared to the BAT's 87 percent sensitivity, their specificities were only 28 and 35 percent respectively - significantly lower than the BAT's 94 percent.
"This indicates their low diagnostic power," research associate of the Department of Pediatrics at CU Medicine Christine Wai Yee-yan said.
"By contrast, our results show that BAT is a superior diagnostic test with very high sensitivity and specificity. This demonstrates that performing even a single diagnostic step involving shrimp-BAT can substantially enhance the accuracy for shrimp allergy diagnosis."
Shrimp allergy is the most common food allergy in Hong Kong. It can cause skin reactions and oral symptoms, and even lead to anaphylaxis, a severe and potentially life-threatening allergic reaction.
One of the patients is a 20-year-old student, Hiu-nam, who first experienced a serious allergic reaction four years ago. She has also experienced shock and breathing difficulties.
She said the shrimp allergy had caused her a lot of stress, recalling having to call for an ambulance in secondary school as she often experienced allergic reactions at school.
Even during gatherings with friends, the 20-year-old said she had to avoid going to Thai or Vietnamese restaurants and her friends would have to use separate chopsticks if there were any seafood dishes, she said.
She also had to constantly pay attention to the ingredients lists of sauces and processed food.
Meanwhile, the CUHK research team has identified three new allergens - hemocyanin, triosephosphate isomerase and fatty acid-binding protein - in giant tiger prawn that are more common in and relevant to the southern Chinese population.
The research team has already registered all three as new shrimp allergens in the Allergen Nomenclature database of the World Health Organization and the International Union of Immunological Societies. It has also patented fatty acid-binding protein and troponin C as novel diagnostic biomarkers for shrimp allergy.
