Antigen and methacholine challenge in children with asthma

Abstract

Antigen inhalation challenges for clinical use have 2 essential purposes in my view. One of these, and perhaps the most important, relates to whether the ultimate goal of therapy is directed toward immunotherapy. The second establishes that the lung either is or is not a target organ, regardless of whether the skin test has demonstrated the presence of specific IgE to the antigen. It follows, therefore, that there should and must be clear-cut indications for antigen challenges, which are not without considerable risk in sensitive individuals. Any asthmatic, who clearly has a seasonal history related to his skin tests, probably does not require any antigen challenges. The role of the challenge is essentially twofold-first, the initial confirmation of the lung being sensitive to the antigen and hence responding as bronchospasm; second, following immunotherapy, the response to another challenge would provide pertinent information as to whether the therapeutic procedure (immunotherapy) is having the required benefit over time and hence whether or not the therapy should be continued. In the case of the patient who has clear-cut seasonal symptoms, related to his skin tests and to few of any other nonimmunologic precipitant mechanisms (parasympathetic hypersensitivity, exercise, cold, hyperirritability of the airways to nonimmunologic stimuli, etc.), antigen challenges should be unnecessary. The clinical and physiologic responsiveness during the next appropriate season would be sufficient to demonstrate the effectiveness of immunotherapy or the lack thereof. However, in those asthmatics in whom clear evidence of an immune system involvement is not apparent, despite positive skin tests, because of a noncorrelating history (such as a lack of increasing asthma during high pollen seasons or the presence of perennial asthma, making clear definition of a particular allergen difficult), antigen challenges may be the only