What is already known about this topic? Shrimp allergy is prevalent, but conventional diagnostic methods including skin prick test (SPT) and specific IgE (sIgE) measurements have low specificity. Testing for tropomyosin improves diagnostic accuracy for shrimp allergy in Caucasians, but this has not been replicated among Asians.What does this article add to our knowledge? BAT has superior diagnostic performance for shrimp allergy than SPT and sIgE measurement. Tropomyosin may not be the most appropriate diagnostic marker in the Chinese population. The IgE crosslinkingeinduced luciferase expression (EXiLE) test can be a good alternative to BAT.How does this study impact current management guidelines? A single step of BAT may replace SPT and sIgE in the diagnosis of patients with clinical history suggestive of shrimp allergy. The EXiLE test can be a suitable alternative with respect to cost and sampling constraint.BACKGROUND: The diagnosis of shellfish allergy currently relies on patient history, skin prick test (SPT), and serum specific IgE (sIgE) quantification. These methods lack sufficient diagnostic accuracy, whereas the gold standard of oral food challenges is risky and burdensome. Markers of reactivity and severity of allergic reactions to shellfish will improve clinical care of these patients. OBJECTIVES: This study compared the diagnostic performance of SPT, sIgE, basophil activation test (BAT), and IgE crosslinkingeinduced luciferase expression (EXiLE) test for shrimp allergy. METHODS: Thirty-five subjects with documented history of shrimp allergic reactions were recruited and grouped according to results of double-blind, placebo-controlled food challenge (DBPCFC). In addition to routine diagnostics, BAT (Flow CAST) and EXiLE test with shrimp extract and tropomyosin were performed. RESULTS: Of 35 subjects, 15 were shrimp allergic with pruritus, urticaria, and itchy mouth on DBPCFC, whereas 20 were tolerant to shrimp. Tropomyosin only accounted for 53.3% of sensitization among subjects with challenge-proven shrimp allergy. BAT using shrimp extract as stimulant showed the highest area under curve value (0.88), Youden Index (0.81), likelihood ratio (14.73), odds ratio (104), and variable importance (4.27) when compared with other assays and tropomyosin diagnosis. Results of BAT significantly correlated with those of EXiLE (r [ 0.664, P < .0001). CONCLUSIONS: BAT is a more accurate diagnostic marker for shrimp allergy than SPT and shrimp sIgE, whereas the EXiLE test based on an IgE crosslinking assay is a good alternative to

Background: Grass carp is the most commonly consumed fish species in Hong Kong. The allergenicity of grass carp and its allergen content are yet to be reported. This study characterized the major allergen in grass carp and investigated its allergenicity. Methods: Sixty-nine subjects with history of IgE-mediated allergic reaction to grass carp were recruited. The protein content in steamed grass carp extract was resolved by SDS-PAGE, and the major allergen was identified by immunoblotting with serum from subjects allergic to grass carp. The identity of allergen was elucidated by mass spectrometry and amino acid sequence obtained by amplifying the specific gene from cDNA library of grass carp. The cross-reactivity between parvalbumins from grass carp and other phylogenetically close (common carp) or commercially important (cod and salmon) species was investigated by competitive inhibition ELISA. Results: A major IgE-binding protein was found at approximately 9 kDa and identified as parvalbumin by immunoblotting and mass spectrometry. Grass carp parvalbumin was more allergenic than common carp, salmon, and cod parvalbumins despite sharing high sequence homology. This newly identified major allergenic parvalbumin isoform from grass carp was registered as Cten i 1 in the World Health Organization and International Union of Immunological Societies allergen database. Conclusions: Grass carp parvalbumin is identified as the major fish allergen in Hong Kong. The strong allergenicity of Cten i 1 contributes to the high IgE reactivity of grass carp. Grass carp, among other fish species, should be considered when managing fish-allergic patients.

Background Clinical management of shrimp allergy is hampered by the lack of accurate tests. Molecular diagnosis has been shown to more accurately reflect the clinical reactivity but the full spectrum of shrimp allergens and their clinical relevance are yet to be established. We therefore sought to comprehend the allergen repertoire of shrimp, investigate and compare the sensitization pattern and diagnostic value of the allergens in allergic subjects of two distinct populations. Methods Sera were collected from 85 subjects with challenge‐proven or doctor‐diagnosed shrimp allergy in Hong Kong and Thailand. The IgE‐binding proteins of Penaeus monodon were probed by Western blotting and identified by mass spectrometry. Recombinant shrimp allergens were synthesized and analyzed for IgE sensitization by ELISA. Results Ten IgE‐binding proteins were identified, and a comprehensive panel of 11 recombinant shrimp allergens was generated. The major shrimp allergens among Hong Kong subjects were troponin C (Pen m 6) and glycogen phosphorylase (Pen m 14, 47.1%), tropomyosin (Pen m 1, 41.2%) and sarcoplasmic‐calcium binding protein (Pen m 4, 35.3%), while those among Thai subjects were Pen m 1 (68.8%), Pen m 6 (50.0%) and fatty acid‐binding protein (Pen m 13, 37.5%). Component‐based tests yielded significantly higher area under curve values (0.77–0.96) than shrimp extract‐IgE test (0.70–0.75). Yet the best component test differed between populations; Pen m 1‐IgE test added diagnostic value only in the Thai cohort, whereas sensitizations to other components were better predictors of shrimp allergy in Hong Kong patients. Conclusion Pen m 14 was identified as a novel shrimp allergen predictive of challenge outcome. Molecular diagnosis better predicts shrimp allergy than conventional tests, but the relevant component is population dependent.