Background It is noteworthy that there is a clear clinical, epidemiological and pathophysiological association between upper and lower airway inflammation in rhinitis and asthma.
Objective The aim of this study was to compare the eosinophil counts in induced sputum and nasal lavage fluids in asthma, checking their association and the accuracy of nasal eosinophilia as a predictor of sputum eosinophilia by a cross-sectional study.
Methods The clinical evaluation, asthma control questionnaire (ACQ), pre- and post-bronchodilator spirometry, nasal and sputum sample was performed. The nasal eosinophilia was analysed by a receiver operating curve and logistic regression model.
Results In 140 adults, the post-bronchodilator forced expiratory volume in 1 s (FEV1) did not differ between patients with or without sputum eosinophilia (0.18). After adjusted for upper airway symptoms, age, ACQ score and post-bronchodilator FEV1, sputum eosinophilia was associated with 52 times increase in odds of nasal eosinophilia, whereas each 1% increase in bronchodilator response was associated with 7% increase in odds of nasal eosinophilia.
Conclusion This study brings further evidence that upper airway diseases are an important component of the asthma syndrome. Furthermore, monitoring of nasal eosinophilia by quantitative cytology may be useful as a surrogate of sputum cytology in as a component of composite measurement for determining airway inflammation.