Assessment of Bronchodilator Responsiveness and Spirometric Patterns in Patients with Rhinitis and Suspected Asthma

Background: Bronchodilation testing (BDT) is routinely used to assess reversibility of airflow limitation. For patients with rhinitis who report asthma-related symptoms but often show preserved spirometry, the clinical patterns associated with bronchodilator responsiveness (BDR) are less clearly described. Understanding these patterns may help clinicians interpret lung function in real-world practice. Methods: We retrospectively analyzed 555 consecutive patients who underwent spirometry and BDT at a single tertiary allergy center. Data on clinical symptoms, allergic status, type-2 inflammatory markers, baseline spirometry results, and BDT outcomes were collected. Associations between symptoms, spirometric indices, and BDR were evaluated. Exploratory analyses examined the relationship between FEV 1 improvements below the conventional ≥ 12% criterion and asthma-related symptoms. Results: Among all participants, 71.9% had allergic rhinitis, and 88.6% reported asthma-related symptoms. BDR was observed across a wide range of baseline spirometry values; 47.2% of BDT-positive patients had FEV 1 ≥ 80% predicted. Small airway indices, especially FEF 5 0 % predicted, were strongly associated with BDR. Wheezing and chest tightness demonstrated clearer physiological correlations than coughing alone did. FEV 1 improvements slightly below the conventional ≥ 12% bronchodilator threshold were also associated with asthma-related symptoms, although these findings were exploratory and not intended as diagnostic criteria. Conclusion: In patients with rhinitis and suspected asthma, airflow variability may be present even when FEV 1 appears preserved. Small-airway parameters and symptom profiles offer a useful context for interpreting BDT results. Modest FEV 1 changes may be clinically relevant and warrant further prospective study. These findings may help clinicians judge when bronchodilation testing is informative during the routine evaluation of suspected airway disease. Keywords: bronchodilator responsiveness, spirometry, rhinitis, asthma, small-airway function, airflow variability