Utility and limitations of objective measures of asthma.

摘要

Asthma is a chronic inflammatory disorder of the airways characterized by airway inflammation, airway hyperrespon-siveness, and variable airways obstruction.1 National estimates show that approximately 22 million people currently have asthma in the United States.2 In 2007, the American Lung Association estimated that the annual economic cost of asthma in the United States was Dollars 19.7 billion.3 From 1980 to 1996, the number of work and school days missed increased by more than 50% to 14 million days each.4 These increases correspond to increased prevalence because the days missed per person have not changed significantly.