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: The protection conferred by influenza vaccination is generally thought to last less than a year, necessitating annual re-vaccination. However, the speed with which influenza vaccine effectiveness (VE) might decline during a year is unknown. This is of particular importance for locations with year-round influenza activity. Methods: We analysed data from a test-negative study of influenza VE in hospitalized children in Hong Kong over five consecutive years. We examined how VE changed by time between vaccination and hospitalisation. Findings: We analysed data on 15,695 children admitted from September 2012 through August 2017. Among study participants, the majority of vaccinations occurred in the final quarter of each year. Influenza admissions occurred year-round with peaks in January through March in most years and a large summer peak in 2016. We estimated that VE against influenza A or B decreased from 79% (95% CI: 64%−88%) for children vaccinated within 0.5 to 2 months, to 60% (95% CI: 46%−71%) within 2 to 4 months, to 57% (95% CI: 39%−70%) within 4–6 months of vaccination, and to 45% (95% CI: 22%−61%) within 6–9 months of vaccination. In separate analyses by type/subtype, we estimated that VE declined by 2–5 percentage points per month. Interpretation: We observed clear evidence of reductions in VE during the 9 months after vaccination in children. Our findings confirm the importance of annual vaccination in children. Influenza vaccines that provide broader and longer-lasting protection are needed to provide year-round protection in regions with irregular influenza seasonality or prolonged periods of influenza activity.

Background Kawasaki disease (KD) is an acute febrile and eruptive disease with systemic vasculitis predominantly affecting young East Asian children. Recent reports showed that children with KD-like disease from KD low prevalence regions had positive SARS-CoV-2 serology despite a negative SARS-CoV-2 polymerase chain reaction (PCR) in respiratory samples. Objectives To describe 3 pediatric Kawasaki Disease patients with false positive SARS-CoV-2 serology. Study design We retrospectively recruited children with KD diagnosed during the COVID-19 outbreak in Hong Kong. Clinical characteristics and laboratory test results including SARS-CoV-2 PCR results were retrieved. We performed a microparticle-based immunoassay for the detection of IgG against nucleoprotein (NP) and spike protein receptor binding domain (RBD), and a microneutralization assay for the detection of neutralizing antibodies. Results Three Chinese children with typical KD were identified. They had no epidemiological links with COVID-19 patients and tested negative for SARS-CoV-2 NPA PCR. They were treated with IVIG and aspirin, and were discharged without complications. Subsequently 2 of them were tested positive against anti-RBD and anti-NP antibodies and 1 was tested positive against anti- RBD antibodies. However, microneutralization assay showed that neutralizing antibodies were absent, suggesting a false-positive IgG result. Conclusion Detection of neutralizing antibodies is recommended to confirm previous SARS-CoV-2 infection in IgG-positive but PCR-negative patients.

Influenza vaccination was effective in preventing hospitalizations in children in Hong Kong.

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.