Allergic rhinitis (AR) may be considered a risk factor for the onset of asthma. Recently, it has been reported that forced expiratory flow between 25% and 75% of vital capacity (FEF_25–75) may predict a positive response to bronchodilation test in asthmatic children. The aim of this study was to evaluate a large group of adult AR patients to investigate the frequency of response to bronchodilation test and FEF_25–75 values.

Methods: One thousand four hundred and sixty-nine consecutive patients suffering from persistent AR were evaluated. Clinical examination, spirometry, and bronchodilation test were performed in all patients.

Results: In this study, 62.9% of patients had reversibility to bronchodilation test and 17.8% had impaired FEF_25–75 values (≤65% of predicted). Impaired FEF_25–75 values associated with longer rhinitis duration may predict reversibility to bronchodilation test (OR = 11.3; P < 0.001). In addition, a FEF_25–75 cutoff value ≤71% of predicted may already discriminate patients with reversibility.

Conclusions: This study highlights that about two-thirds of patients with persistent AR may be considered at risk of becoming asthmatic. This finding should be adequately considered as a precocious spirometry may allow the early detection of patients prone to develop asthma and consequently to treat them.