REPRODUCIBILITY OF THE EFFECTS OF INTRANASAL RAGWEED CHALLENGES IN ALLERGIC SUBJECTS

Background: Intranasal allergen challenges have been used to study the pathogenesis of disease expression, to evaluate the efficacy of thera pies and to make diagnosis of allergic status. Few data, however, are available regarding the reproducibility of the responses to such provo cative challenges. Objective: The purpose of this study was to evaluat e the reproducibility of selected responses of allergic subjects to in tranasal pollen challenge. Methods: Eighteen adults with ragweed aller gy completed three dose-response challenge sessions at a minimum inter val of 1 week. Sessions were single blinded and randomized to include two intranasal ragweed challenges (doses 10, 100, and 1000 PNU) and on e placebo challenge conducted out of the ragweed season. Additionally, 12 of these subjects completed a third ragweed challenge session cond ucted during the ragweed season. Following administration of each dose , symptoms were scored, sneezes counted, and nasal patency measured by active posterior rhinomanometry. Total nasal secretion weight for eac h session was measured. Results: For all measures, average dose respon se curves were identical for the two extra-seasonal ragweed challenges and these were significantly different from those of the placebo chal lenge session. Intra-individual responses to the two ragweed challenge s were highly correlated between sneeze count and secretion weight, an d were moderately correlated for objective and subjective measures of rhinorrhea and congestion. No significant increases in these responses were observed for the intra-seasonal ragweed challenge session. Concl usions: These results document a reproducible symptomatic and physiolo gic response to intranasal ragweed challenge.