Examination of sputum for eosinophils and measurement of exhaled
nitric oxide have been proposed as noninvasive methods of assessing airway
inflammation in
asthma. The use of these tests in the evaluation of patients with
occupational asthma has not been reported. This study investigated the changes in sputum eosinophils and exhaled NO before and at intervals after inhalation challenge with
plicatic acid in patients with suspected western red cedar
asthma. Of 17 subjects who underwent challenge, nine had a positive bronchoconstrictor reaction (responders) and eight had a negative reaction (nonresponders). At 6 and 24 h after
plicatic acid challenge, there was a significant increase in sputum eosinophils among responders, which was inversely related to the fall in forced expiratory volume in one second (FEV1) at 6 h. An increase in sputum eosinophils was also found in three nonresponders. Levels of exhaled NO increased at 24 h after challenge with
plicatic acid in both responders and nonresponders, being significant only in nonresponders. No correlation was found between the increase in
nitric oxide and the magnitude of the functional changes in the airways. There were significant correlations between the degree of sputum
eosinophilia and the level of exhaled NO before and after
methacholine and
plicatic acid challenge. In conclusion, the late asthmatic reaction induced by
plicatic acid in patients with western red cedar
asthma is associated with an increase in sputum eosinophils. The usefulness of measuring sputum eosinophils and exhaled
nitric oxide in the clinical evaluation of patients with suspected
occupational asthma caused by low molecular weight compounds has yet to be determined.