Bronchial Responsiveness in Children Exposed to Atmospheric Pollution in Hong Kong: Histamine Challenge Test
Consent for use of histamine challenge tests was obtained after submission of a proposal to the institution’s ethics committee.
The children received a bronchial challenge by histamine according to the method of Yan et al. Those children who had experienced an upper respiratory tract infection in the past 10 days with symptoms on the day of examination, confirmed by a physician, or whose FEVi was less than 60 percent of predicted, were excluded. The endpoint of the challenge was either a reduction of 20 percent or more of FEV i from baseline, or inhalation of the last dose of histamine. At the conclusion of the test, each child was examined for any respiratory discomfort, and nebulized salbutamol was given to any who had a reduction of 20 percent or more in FEV ь or if there was chest tightness Here zyrtec tablets. The FEV i was then measured at 2- to 3-min intervals until it returned to within 90 percent of the baseline.
The method of Abramson et al was used to examine the data. The PD20 was defined as the cumulative dose of histamine causing a 20 percent decrease in FEVi. Bronchial hyperreactivity (BHR) was considered to be severe if PD20 was less than 0.10 /nmol, moderate if 0.10 to 0.79 jrniol, mild if 0.80 to 3.19 jimol, slight if 3.20 to 7.79 jumol, and none if 7.80 /шю 1 or more. The FEV i aggregated dose response slopes used for the assessment of BR and other anthropometric and lung function measurements were compared by Student’s t tests. Comparison of respiratory symptoms and BHR between districts was made using chi-square tests.
Adjustment for gender, age, school, session attended (morning/ afternoon), education of father, living quarter type (public housing/others), and exposure to passive smoking (defined as one, two, or more household members smoking) was made using a generalized estimating equations (GEE) procedure for the BR slope and for BHR based on the two categories of PD20<3.2 /umol and PD20<7.8 дто1. Adjustment for the effects due to cluster sampling was made by introducing intraclass correlation in the GEE procedure.