Role of forced expiratory flow at 25–75% as an early marker of small airways impairment in subjects with allergic rhinitis

A close link exists between allergic rhinitis and asthma. Small airway disease (SAD), defined by a reduction in forced expiratory flow at 25–75% of the pulmonary volume (FEF_25–75) and normal spirometry (normal forced expiratory volume at 1 second [FEV₁], forced vital capacity [FVC], and FEV₁/FVC ratio), may be a marker for early allergic or inflammatory involvement of the small airways in subjects with allergic diseases and no asthma. The aim of this study was to determine if there is a relationship between SAD, the outcome variable, and several allergic predictors in patients without asthma but with allergic rhinitis. A cross-sectional study was performed. Two hundred eleven midshipmen attending the third and fifth course of the Navy Academy of Livorno were screened. Fifty-eight midshipmen showed slight spirometric anomalies. Thus, they were referred to the Navy Hospital of La Spezia for standardized tests: skin-prick test, nasal cytology, spirometry, and methacholine bronchial challenge. A reduced FEF_25–75 was arbitrarily defined as <80% of predicted. All 58 subjects had a normal FEV₁, FVC, and FEV₁/FVC ratio. Twenty subjects had a reduced FEF_25–75, consistent with the definition of SAD. A mean value of FEF_25–75 of 70.3 (SD, 8.5) was measured in patients with a reduced FEF, and it was 108.0 (SD, 14.3) in patients with preserved FEF_25–75. All the candidate allergic predictors appeared to be strongly associated with a reduced FEF_25–75. The proportion of subjects with reduced FEF_25–75 appeared to increase with increasing severity of the allergic predictors, and, correspondingly, the mean value of FEF_25–75 appeared to decrease. This study provides evidence that there is a relationship between SAD and allergic parameters such as nasal symptoms and eosinophils.