Evaluation of asthma responses in ALYATEC EEC in birch allergic rhinitis (AR) with and without asthma

Abstract

Background: Birch pollen mainly induces allergic rhino conjunctivitis. There is a considerable discordance between patient reported asthma and responses during bronchial allergen challenge.

Objective: To analyze asthma responses to birch allergen in ALYATEC Environmental Exposure Chamber (EEC) in patients with and without asthma.

Methods: 30 patients with AR without asthma and 24 with GINA 1 birch-related asthma, were exposed to 60 ng/m3 of Bet v 1 in EEC. Patients must have positive skin prick tests (SPT) and birch specific IgE at selection. Exposures lasted 4 hours to assess rhinitis responses in patients with AR and 1 hour for asthma only. Nasal response was defined as Total Nasal Symptom Score (TNSS) ≥ 5, Early Asthma Response (EAR) as 20% drop in FEV1 and Late Asthma Response as 15% drop in FEV1, 3 to 24 hours after EAR.

Results: Among patients with AR without asthma, 53.3% had EAR and 16.6% LAR. The mean time to obtain EAR was 77 min [range 30-240]. Dual asthmatic responses occurred more frequently in patients with early nasal responses (mean Δ TNSS=5.76±1.1). EAR occurred in all asthmatics within 34 min [15-60], followed by 62.5% of LAR. The severity of asthma response was assessed by the maximum drop in FEV1, with 25.0 (±4.66) for EAR and 19.9 (±3.18) for LAR. Sensitization to birch was similar in both populations; SPT mean wheal diameter of 8.68 mm for AR without asthma and 7.81 mm in asthmatics.

Conclusion: Birch-related asthma seems underestimated in patients with AR. Birch allergen induced dual bronchial responses in more than 50% of asthmatics. These results are comparable to those obtained in mite asthmatics, suggesting that birch is as asthmogenic as mite allergen.