Cross-reactive carbohydrate determinant (CCD) inhibition test can help identify false positive for plant allergen sIgE caused by CCD

Background: Pollen allergens are important inhaled allergens and can cause respiratory allergic diseases, especially seasonal allergic rhinitis and asthma. The study analyzed the sensitization of pollen allergens in south China and discussed the effect of CCD inhibitor on the results of sIgE test of pollen allergens. Method: 213 allergic rhinitis or asthma patients who were IgE positive to least two common inhaled allergens were recruited. Serum samples were analyzed for IgE against tree mix (willow/poplar/elm Tree), common ragweed, mugwort, humulus scandens, peanut, soy, and cross-reactive carbohydrate determinants (CCD) and specific IgE-binding inhibition experiments were performed. Results: 83 patients (39.0%) were plant allergen sensitization (sIgE positive for any of the above six allergens was defined as plant allergen sensitization, PAS), and 57.8% of PAS patients were positive to CCD-sIgE. PAS subjects were more often sensitized to CCD, known to be cross-reactive between grass and seeds. CCD inhibited binding to all pollen and seed allergen by 73% to 100%, see figure 1. The highest inhibition rate was obtained for Humulus scandens, followed by mugwort and peanut (both 85.2%), common ragweed (81.5%), soy(80.0%) and tree mix (73.0%). It was surprised to find that all sIgE against to pollen and seeds from 23 PAS patients were turned to negative after CCD inhibition. Conclusion: More than 73% plant allergens-sIgE were eliminated into negative after CCD inhibition experiment, suggesting majority the plant allergic patients in southern China. CCD inhibition test should be used in clinical diagnosis, which can help to avoid misdiagnosis of plant allergens.