BACKGROUND: Nasal hyperreactivity is a prominent feature of allergic rhinitis. Variation in nasal hyperreactivity with different challenge agents in and out of the pollen season has not been examined. OBJECTIVE: We sought to compare nasal hyperreactivity with different challenge agents before, during, and after the pollen season. METHODS: Grass pollen-monosensitized patients performed cumulative-dose challenges with nasal AMP (25-800 mg · mL(-1)) and histamine (0.25-8 mg · mL(-1)) before, during, and after the grass pollen season. Outcomes included the provocative concentration of agent causing a 30% decrease in the peak nasal inspiratory flow (PNIF) (PC(30)), recovery profile, and diary cards. RESULTS: Nineteen participants completed per protocol. AMP PC(30) values for PNIF worsened by 1.33 (95% CI, 0.20-2.44; P = .02) doubling dilutions during the season but recovered after the season. The AMP recovery curve showed a -14.39% difference (95% CI, -21.11% to -7.66%; P < .001) during the season and remained abnormal after the season (-8.05% [95% CI, -14.78% to -1.33%; P < .05). Histamine PC(30) values did not change during the season, but recovery was prolonged by -14.47% (95% CI, -22.19% to -6.76%, P < .001), returning to baseline values after the season. Nasal symptoms, domiciliary PNIF, and serum eosinophil-derived neurotoxin levels returned to baseline values after the season. CONCLUSIONS: There is a reduction in AMP PC threshold but not histamine PC threshold during the pollen season, indicating that AMP is a more sensitive indicator of allergic inflammation. The residual hyperreactivity to nasal AMP, but not histamine, outside of the pollen season, seen as a persistently prolonged recovery curve, suggests the presence of primed airway mucosal mast cells, even in asymptomatic patients, and persistent activation of mediator pathways, such as cysteinyl leukotrienes. Copyright Â
BACKGROUND: Nasal hyperreactivity is a prominent feature of allergic rhinitis. Variation in nasal hyperreactivity with different challenge agents in and out of the pollen season has not been examined. OBJECTIVE: We sought to compare nasal hyperreactivity with different challenge agents before, during, and after the pollen season. METHODS: Grass pollen-monosensitized patients performed cumulative-dose challenges with nasal AMP (25-800 mg · mL(-1)) and histamine (0.25-8 mg · mL(-1)) before, during, and after the grass pollen season. Outcomes included the provocative concentration of agent causing a 30% decrease in the peak nasal inspiratory flow (PNIF) (PC(30)), recovery profile, and diary cards. RESULTS: Nineteen participants completed per protocol. AMP PC(30) values for PNIF worsened by 1.33 (95% CI, 0.20-2.44; P = .02) doubling dilutions during the season but recovered after the season. The AMP recovery curve showed a -14.39% difference (95% CI, -21.11% to -7.66%; P < .001) during the season and remained abnormal after the season (-8.05% [95% CI, -14.78% to -1.33%; P < .05). Histamine PC(30) values did not change during the season, but recovery was prolonged by -14.47% (95% CI, -22.19% to -6.76%, P < .001), returning to baseline values after the season. Nasal symptoms, domiciliary PNIF, and serum eosinophil-derived neurotoxin levels returned to baseline values after the season. CONCLUSIONS: There is a reduction in AMP PC threshold but not histamine PC threshold during the pollen season, indicating that AMP is a more sensitive indicator of allergic inflammation. The residual hyperreactivity to nasal AMP, but not histamine, outside of the pollen season, seen as a persistently prolonged recovery curve, suggests the presence of primed airway mucosal mast cells, even in asymptomatic patients, and persistent activation of mediator pathways, such as cysteinyl leukotrienes. Copyright Â