Peak flow variability and sputum eosinophilia in allergic rhinitis

Area of Science:

• Pulmonary Medicine
• Allergy and Immunology
• Respiratory Physiology

Background:

• Allergic rhinitis can present with airway hyperresponsiveness and increased diurnal peak expiratory flow (PEF) variation in non-asthmatic individuals.
• The specific features driving these physiological alterations in allergic rhinitis patients without asthma remain unclear.

Purpose of the Study:

• To investigate the presence of asthmatic airway inflammation markers in non-asthmatic subjects with allergic rhinitis and methacholine hyperresponsiveness.
• To determine if eosinophilic inflammation is a key feature in these individuals.

Main Methods:

• Studied 40 non-asthmatic adults: 11 with allergic rhinitis and methacholine hyperresponsiveness, 20 with allergic rhinitis and normal responsiveness, and 9 healthy controls.
• Induced sputum using hypertonic saline for differential cell counting.
• Monitored daily peak expiratory flow (PEF) for 14 days to calculate PEF variation (amplitude % mean).

Main Results:

• Subjects with allergic rhinitis and methacholine hyperresponsiveness exhibited significantly higher peak expiratory flow variation compared to other groups.
• Induced sputum revealed significantly higher eosinophil counts in subjects with allergic rhinitis and hyperresponsiveness (7.3%) versus allergic rhinitis alone (2.5%) and healthy controls (1.0%).

Conclusions:

• Eosinophilic inflammation is present in allergic rhinitis patients with airway hyperresponsiveness, even in the absence of asthma symptoms.
• Bronchial eosinophilia may not be sufficient on its own to manifest as clinical asthma symptoms.