Nasal Eosinophils Display the Best Correlation with Symptoms, Pulmonary Function and Inflammation in Allergic Rhinitis

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Abstract
Background: The pathogenesis of allergic rhinitis and its link with asthma are well known. Nevertheless, a complete cross-sectional evaluation of the usually available clinical, functional and immunological parameters has never been made. We assessed nasal symptoms and flow, cytology, cytokines, pulmonary function and methacholine positivity in a large number of patients with pure pollinosis. Methods: Young men presenting at a military hospital for routine follow-up were recruited for the study. They had to suffer from rhinitis alone (without asthma) for at least 2 years and had to have a positive skin prick test to pollens only. During the pollen season, they underwent symptom evaluation, measurement of nasal flow, nasal scraping and lavage (cell count and assay for IL-4, IL-5, IL-8 and IFNγ), pulmonary function tests and methacholine challenge. Results: Fifty subjects (23.7 ± 4.9 years old) were enrolled. All patients had high clinical scores (9.5 ± 1.6) and inflammatory cells (eosinophils: 10.5 ± 4 and neutrophils 21.3 ± 6) and low nasal flow (482 ± 111 ml/s). We found that the number of eosinophils in nasal scrapings highly correlated with all the above-mentioned parameters, including nasal flow, cytokines and spirometric values. A significant positive correlation was found between all inflammatory cells and all cytokines. IL-8, IL-4 and neutrophils displayed only a partial correlation with pulmonary parameters (FEV1, FVC and FEF25–75%), at variance wit IL-5 and eosinophils. Methacholine test positivity significantly correlated with the number of eosinophils in the nasal smear. Conclusion: Eosinophils in the nasal smear display the best correlation with all the clinical and immunological parameters in allergic rhinitis and also correlate well with methacholine response.