The Nasal Smear for Eosinophils, Its Value, and Its Relation to Nasal Mucosal Eosinophilia in Allergic Rhinitis

Introduction: There is no single test as a gold standard for the diagnosis of allergic rhinitis (AR). The aim of this study was to assess the usefulness and validity of nasal smear as a quick, easy and inexpensive diagnostic method for diagnosis of allergic rhinitis. Materials and Methods: This study was conducted in a university hospital setting. Nasal smears were taken from 39 patients with a clinical history of nasal allergy and a positive skin prick test to at least one aeroallergen as well as 26 controls without any history and negative test. Biopsy specimens from the inferior turbinate as well as nasal smears of 19 cases including 9 patients and 10 controls with the same criteria were taken. Nasal smears and biopsy slides were stained with Giemsa and Hematoxilin-Eosin and were examined blindly by two separate pathologists. Results: Fifty one percents of the patients and 11.5% of the controls showed eosinophilia in their nasal smear (≥10% eosinophils, P=0.001). The sensitivity of nasal eosinophil count as a diagnostic test for AR was 51.3% with a specificity of 88.5%, a positive predictive value of 87% and a negative predictive value of 54%. Eosinophilia in nasal biopsies was found in 44% and 30% of allergic patients and controls respectively. There was no significant correlation between symptoms or positive skin tests with either smear eosinophilia or tissue eosinophilia. Conclusion: Evaluation of eosinophils in nasal smear is an insensitive but fairly specific test for the diagnosis of allergic rhinitis. It seems that the nasal secretions and nasal tissue represent two distinct cellular compartments.