Determinants of airway response to challenge with distilled water in a population sample of children aged 7 to 10 years old.

We challenged 446 schoolchildren and measured the percent decrease in FEV1 following 10 min of tidal inhalation of UNDW. Assessment tools for respiratory symptoms and atopy were questionnaire and skin testing, respectively. A previous diagnosis of asthma was most strongly associated with a positive airway response (defined as a fall in FEV1 greater than or equal to 10 percent. A positive response was also associated with atopy, presence of cough, cough during night, or any respiratory symptom. A child's age and the prechallenge FEF75% also explained response to distilled water indicating less responsiveness for older children and those with relative greater airway diameter. For the previous diagnosis of asthma, a positive distilled water challenge test had a sensitivity of 36 percent and a specificity of 92 percent. We conclude that a significant relationship between airway response to distilled water, asthma and symptoms suggestive for asthma exists for a childhood population sample.