Study objective: To determine the prevalence of
positive results for methacholine challenge tests in asymptomatic
Reserve Officer Training Corps (ROTC) cadets with no history of
Design: Prospective, blinded cohort comparison
Setting: Pulmonary diseases clinic in a US Army
tertiary-care medical center.
Patients: One hundred
three college students who were undergoing a physical examination
before entering active duty. Group 1 subjects, 58 men and 5 women with
an average age of 22.7 years, had no symptoms or personal history of
asthma. Group 2 patients, 34 men and 6 women with an average age of
22.2 years, had a history or recent suggestive symptoms of asthma.
Interventions: Methacholine challenge testing using
concentrations of 0.025, 0.25, 2.5, 10, and 25 mg/mL for a total dose
of 188 inhalation units or until FEV1 had declined by
Results: Group 2 had significantly more
patients with positive results for methacholine challenge tests
or reversible airflow obstruction at baseline (23 of 40 patients[
57.5%]) than group 1 (8 of 63 patients [12.7%]; p < 0.05).
The cadets in group 1 with positive results for methacholine challenge
tests reacted with a 20% decline in FEV1 at the following
concentrations: 25 mg/mL (188 IU), 2 patients; 10 mg/mL (64 IU), 4
patients; and 2.5 mg/mL (13.8 IU), 2 patients. Using values calculated
for the provocative concentration of a substance causing a 20% fall in
FEV1 and the new American Thoracic Society criteria, four
patients would have borderline bronchial hyperresponsiveness (4 to 16
mg/mL) and three patients (4.8%) would have mild bronchial
hyperresponsiveness (1 to 4 mg/mL).
Conclusions: Asymptomatic US Army ROTC cadets with no
history of asthma have possible false-positive responses to
methacholine at concentrations > 0.25 mg/mL.