D2.113 - Comparison of Non-Asthmatic Allergic Rhinitis Patients with Normal and Low FEF25–75 Levels

Allergic rhinitis (AR) is one of the most common chronic allergic diseases in general population and can significantly impair patients’ quality of life. Recent studies and evidence emphasize that rhinitis and asthma should be considered as a single airway disease. Although symptoms in most patients appear to be limited to the upper respiratory tract, subclinical involvement of the lower airways may be present. Forced expiratory flow between 25% and 75% of vital capacity (FEF25–75) is one of the pulmonary function test parameters used to evaluate small airway disease and is important for assessing early airway involvement. The aim of this study was to determine whether underlying small airway obstruction or the risk of developing asthma can be predicted in patients with pure AR, and to investigate the relationship between sensitization profiles and airway involvement.

Patients aged >18yr and older who presented with symptoms of allergic rhinitis between January 2023 and September 2025, with no symptoms of asthma and had positive skin prick test or specific IgE results were included in the study. Patients were retrospectively reviewed. Data recorded included age, sex, body mass index, presence of concomitant allergic diseases, smoking status, presence of pets at home, rhinitis–conjunctivitis symptoms, season and duration of symptoms, and the presence of anosmia or nasal polyps. Pulmonary function test parameters (FEV₁, FEV₁/FVC, and FEF25–75, sensitizing allergen(s), blood eosinophil, basophil, and total IgE levels, as well as treatments received by the patients were recorded. Statistical analyses were performed using IBM SPSS version 26.

Patient groups with FEF₍25–75₎ levels below and above 70% were compared according to the recorded characteristics. Significant differences were observed between the groups in terms of female sex (p < 0.001), presence of pets at home (p = 0.01), tree pollen sensitization (p = 0.002), age, and FEV₁ levels.

In this study, patients with allergic rhinitis and low FEF₍25–75₎ levels were more likely to be of older age, female sex, have lower FEV₁ levels, have pets at home, and show sensitization tree pollen. Adding FEF₍25–75₎ assessment to routine spirometry in patients with allergic rhinitis may be useful for earlier identification of individuals at higher risk of developing asthma. Patients with advanced age, female sex, low FEV₁ levels, and tree pollen sensitization may require closer follow-up. The strengths of this study include its focus on lower airway involvement in patients with rhinitis and the combined evaluation of clinical and immunological parameters. Limitations include its retrospective and single-center design, the variability of FEF₍25–75₎ as a spirometric parameter, and the lack of prospective follow-up data to determine whether patients with low FEF₍25–75₎ subsequently develop asthma.

Low FEF₍25–75₎ levels in patients with allergic rhinitis may indicate silent involvement of the small airways. This finding may contribute to the early identification of patients at risk for developing asthma. Future prospective, multicenter studies are needed to confirm this relationship.