Methods: The ACT is a 4-zone facility holding up to 100 seats in a series of elevated rows. Pollen was injected into the air supply and blown into the facility through ducts located across the top of the front wall. Pollen concentrations in the ACT were measured using laser particle counters (LPC) and impact samplers (IS). For the technical validation, LPC were used to assess the long-term stability of pollen levels; IS were used to determine pollen uniformity at 15 locations in the room. For the clinical validation, thirty ragweed allergic subjects were exposed to ragweed for 4 hours on two separate days to assess the reproducibility of rhinitis symptoms. Pollen was monitored at 30 min intervals by 3 IS located in the patient seating area.
Results: Three-hour stability results were comparable for LPC (5107 ± 244 g/m3) and IS (4858 ± 414 g/m3). Uniformity testing gave an average ragweed concentration of 4,622 g/m3; with a front-to-back SD of ± 544 g/m3 and a side-to-side SD of ±333 g/m3.
For the subject challenges, the mean 4-hour pollen concentration was 3,929 g/m3 for Day 1 and 4,099 g/m3 for Day 2. Plateau (2-4 hour) nasal symptom scores were 6.28 ± 1.49 and 6.19 ± 2.14, p=0.74, respectively. Ocular symptom scores were 2.82 ± 1.4 and 2.93 ± 1.82, p=0.59, respectively.
Conclusion: The validation studies showed that ragweed pollen levels in the ACT could be maintained stable over long periods. Subjects responded to the allergen challenge with reproducible rhinitis symptoms on different days. Facilities such as the ACT can provide a suitable means to test new allergy medications.