Late asthmatic reactions to occupational sensitizing agents: Frequency of changes in nonspecific bronchial responsiveness and of response to inhaled β 2-adrenergic agent

Abstract

Late asthmatic reactions have been demonstrated, generally, to increase bronchial responsiveness and are believed to respond poorly to inhaled bronchodilator. To assess the frequency of changes in bronchial responsiveness, we reviewed the records of 101 subjects with late asthmatic reactions and of 63 subjects with isolated immediate reactions after specific inhalation challenges to various occupational agents. These subjects had undergone nonspecific inhalation challenges to histamine or methacholine on a control day and after the late reaction when FEV 1 had returned to ± 10% baseline. We also reviewed 99 cases of subjects with late reactions who were administered an inhaled β 2- agent (albuterol, 200 μg) during the late reaction. Fifty-seven/101 (56%) subjects with late reactions and 24/63 (38%) subjects with isolated immediate reactions demonstrated a twofold or greater change in provocative concentration of histamine or methacholine causing a 20% change in FEV 1 (PC 20) from baseline ( p = 0.02; odds for the presence of significant changes in PC 20 in subjects with late reactions, 56%; odds for the absence of significant changes in PC 20 in subjects with immediate reactions, 62%). Changes in FEV 1 >20% after administering albuterol at the time of the late reactions occurred in 78% of the subjects tested; in 66%, FEV 1 returned to >90% baseline. This retrospective study demonstrates that changes in bronchial responsiveness after late reactions are not constant and do not appear to distinguish satisfactorily late from immediate reactions. Furthermore, late reactions respond well to β 2-agonist. Because late asthmatic reactions and the associated changes in bronchial responsiveness and their assumed poor response to bronchodilators have been related to airway inflammation, our results might suggest that inflammatory changes, which were not directly assessed in this study, are not unique and specific to late reactions. This hypothesis, nevertheless, warrants testing in a prospective study.