ABSTRACT
Tests of airway hyperresponsiveness (AHR) using stimuli that act indirectly
to cause airway narrowing are becoming increasingly popular to identify and monitor asthma (1-3). AHR to an indirect stimulus may identify a
person with active airway inflammation who would likely benefit from treat-
ment with inhaled corticosteroids (ICS). Identification of AHR is of signif-
icant clinical value particularly if the person has normal spirometry and/or
few symptoms, is well controlled, or has a past history of asthma. The
documentation of a response to an indirect stimulus, within the normal
healthy range, indicates quiescence of asthma and provides an end-point
for treatment and a starting point for back titration of inhaled steroids. The indirect stimuli include exercise, eucapnic voluntary hyperpnea
(EVH), hypertonic (4.5%) saline, mannitol, and adenosine monophosphate. All these stimuli have been used to identify AHR and to assess its severity
and to monitor response to treatment with inhaled steroids (4-11). Some
have been used to monitor AHR in response to a change in environmental
allergen exposure (12) or change due to seasonal exposure (13-15), and
some have been used in epidemiological studies to document prevalence of active asthma (16-22).
