Asthma phenotypes in Niue Islanders

Objective: The aim of this study was to identify asthma phenotypes in patients of Niue Island ancestry that might be suitable for susceptibility gene mapping studies. Methodology: Two hundred and sixteen Niue Islanders with physician-diagnosed asthma that was not secondary to other medical conditions were recruited through community organisations. Fifty-one of the subjects with asthma were resident on Niue Island and 165 in New Zealand. Each subject was interviewed and tested for atopy, serum [IgE] (5% quantile, median, 95% quantile) and lung function. Results: There were two groups of subjects defined by an age of onset of asthma less than 12 years of age (childhood- onset, boys:girls 64:65) and greater than 12 years of age (adult-onset, men:women 11:76). A positive response (wheal > 3 mm) to at least one aeroallergen was seen in 181 patients, with 168/181 (92.8%) responding to house dust mite. Twenty-eight subjects with asthma were non-atopic (no detectable wheal) and the atopy status of seven subjects with asthma could not be determined (wheal < 3 mm). In childhood-onset asthma, serum IgE levels were higher (P < 0.0001) in subjects with atopic than in subjects with non-atopic asthma. In adult-onset asthma, serum IgE levels were higher (P < 0.0001) in subjects with atopic asthma than in either subjects with non-atopic asthma or matched non-atopic subjects without asthma. The asthma phenotypes in Niue Island and New Zealand residents were similar. Conclusions: Both atopic and non-atopic asthma phenotypes exist in Niue Islanders resident in Niue and New Zealand. The potential for mapping asthma susceptibility genes in this isolated population is discussed.