Symptoms of asthma, methacholine airway responsiveness and atopy in migrant Tokelauan children.

503 migrant Tokelauan children between five and 15 years resident predominantly in Porirua and the Hutt Valley were surveyed as part of a study of asthma prevalence in a recently migrant population. The survey consisted of domiciliary interview with parents, physical examination, assessment of bronchial hyperresponsiveness and atopy, by allergen skin prick testing. Forty-three children (8%) had a history of wheezy breathing or asthma. 160 children (32%) had evidence of increased airway responsiveness defined as a PD20 (provocative dose of methacholine causing a less than or equal to 20% fall in FEV1, of less than or equal to 12.2 mumoL methacholine). Of the 43 children with a history of asthma, 40 (93%) had evidence of bronchial hyperresponsiveness, 36 (84%) were atopic and 35 (81%) had both bronchial hyperresponsiveness and atopy. Forty-five children (9%) were found to be wheezing on the day of examination only 16 of these had a history of wheezing. Twenty seven of the wheezing children demonstrated bronchial hyperresponsiveness and 22 of these were atopic. Of the 18 children wheezing but with no evidence of bronchial hyperresponsiveness only six were atopic. These contrasting findings suggest differences in the cause of symptoms among the children. Regional differences were observed for the prevalence of symptoms and signs of asthma, bronchial hyperresponsiveness and atopy. Hutt Valley Tokelauan children exhibited a higher prevalence than the Porirua children. Migrants to the Hutt Valley and Porirua are from different atolls, and these differences raise the possibility of a genetic influence on the development of asthma.