PURPOSE: Cockroaches are an important indoor allergen source causing allergic rhinitis and asthma. The aim of this study was to investigate the cockroach prevalence in mainland China and the cross-reactivity of IgE between cockroach and house dust mite allergen in Chinese patients.
METHODS: The cockroach sensitization pattern was based on a skin prick test (SPT) obtained from a national multicenter prevalence study, where 6304 patients from 25 allergy centers across China participated. Factors, including different regions of China, age, gender and the correlations between the American and German cockroaches and house dust mite Der p were investigated. Eighteen out of 1236 clinical sera from south China were selected to perform the cross-inhibition assay between house dust mites and cockroaches.
RESULTS: Totally 25.7% of patients were SPT positive to the American cockroach (Periplaneta Americana, Per a) and 18.7% SPT positive to the German cockroach (Blattella germanica, Bla g). The prevalence of positive cockroach SPT was higher in southern than in northern China, higher in adults than in children, and higher in males than in females. Patients had relatively low levels of cockroach SPT reactions, mainly class 1 or 2. Of the SPT positive cockroach patients, 88% were also SPT positive to house dust mite (Dermatophagoides pteronyssinus, Der p). An IgE cross-inhibition study confirmed that Der p sensitization could cause false positive SPT reactions against cockroach.
CONCLUSIONS: A relatively high prevalence of cockroach sensitivity was found in mainland China. However, a cross-inhibition study showed that only a small number of patients appear to have Bla g and/or Per a as primary sensitizing source. The importance of cockroaches as a risk factor for sensitization and triggers of allergic symptoms in mainland China needs to be further investigated.
CLINICAL IMPLICATIONS: There was strong IgE cross-reactivity between the German and American cockroach species, which should be taken into consideration when performing specific diagnosis and antibody-based environmental allergen analyses. Cross-inhibition studies suggested that the cockroach was the primary sensitizing source in a small number of Chinese allergic patients. Serum IgE that recognized allergens from both Bla g, Per a and Der p, due to cross-reactivity, was present in a relatively high proportion of patients and should be taken into consideration when performing specific diagnosis.
DISCLOSURE: The following authors have nothing to disclose: Baoqing Sun, Xuxin Lai, Birgitte Gjesing, Michael Dho Spangfort, Nanshan Zhong
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