Table 2.
Comparison of the features of the nasal and the bronchial allergen challenge performed for clinical purposes.
| Nasal Allergen Challenge | Bronchial Allergen Challenge | |
|---|---|---|
| Standardized for clinical use | Yes | No |
| Need to withdraw ICS | No | Yes |
| Minimum FEV1 required | Flexible as long as the bronchial disease is sufficiently controlled | 70% |
| Primary diagnostic use | Allergic rhinitis, local allergic rhinitis and dual allergic rhinitis [53] | Allergic asthma and local allergic asthma |
| Recommended monitoring system | Symptoms score (subjective) and objective measurement of the nasal patency (e.g., by acoustic rhinometry) | Bronchial obstruction by spirometry. Possible: symptom score, AHR (e.g., by methacholine challenge) and inflammation (e.g., FeNO) |
| Cutoff points for positivity | More defined | Less defined |
| Safety in asthma patients | High | Moderate |
| Reproducibility | High [54,55] | High |
| Length of the procedure including observation period | 30 min to 1 h | From 7 to 24 h |
| Sample collection in connection to the procedure | Nasal lavage or secretions. Mucosal scraping, brushing or biopsy. FnNO. | Induced sputum, BAL. Mucosal brushing or biopsy. FeNO. |
| Capacity of phenotyping the united airways disease | Variable (depends on the phenotype) | Unknown |
ICS: inhaled corticosteroids; AHR: airway hyperresponsiveness; BAL: bronchoalveolar lavage; FeNO: fractional exhaled nitric oxide; FnNO: fractional nasal nitric oxide; FEV1: forced expiratory capacity in the 1st second.